Spectrally selectiveB1-insensitiveT2 magnetization preparation sequence

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Abstract

AT2 magnetization-preparation (T2 Prep) sequence is proposed that is insensitive toB1 field variations and simultaneously provides fat suppression without any further increase in specific absorption rate (SAR). IncreasedB1 inhomogeneity at higher magnetic field strength (B0 ≥ 3T) necessitates a preparation sequence that is less sensitive toB1 variations. For the proposed technique,T2 weighting in the image is achieved using a segmentedB1-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 yieldsT2 weighting with bothB1 andB0 insensitivity. To simultaneously suppress fat signal (at the cost ofB0 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, 2009. © 2009 Wiley-Liss, Inc.

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