Spectrally Selective B1-Insensitive T2 Magnetization Preparation Sequence

A T-2 magnetization-preparation (T-2 Prep) sequence is proposed that is insensitive to B-1 field variations and simultaneously provides fat suppression without any further increase in specific absorption rate (SAR). Increased B-1 inhomogeneity at higher magnetic field strength (B-0 >= 3T) necessitates a preparation sequence that is less sensitive to B, variations. For the proposed technique, T-2 weighting in the image is achieved using a segmented B-1-insensitive rotation (BIR-4) adiabatic pulse by inserting two equally long delays, one after the initial reverse adiabatic half passage (AHP), and the other before the final AHP segment of a BIR-4 pulse. This sequence yields T-2 weighting with both B-1 and B-0 insensitivity. To simultaneously suppress fat signal (at the cost of B-0 insensitivity), the second delay is prolonged so that fat accumulates additional phase due to its chemical shift. Numerical simulations as well as phantom and in vivo image acquisitions were performed to show the efficacy of the proposed technique. Magn Reson Med 61:1326-1335, 2009. (C) 2009 Wiley-Liss, Inc.