Advanced three-dimensional tailored RF pulse for signal recovery in T 2 *-weighted functional magnetic resonance imaging

Abstract

T 2 * -weighted functional MR images are plagued by signal loss artifacts caused by susceptibility-induced through-plane dephasing. We present major advances to the original three-dimensional tailored RF (3DTRF) pulse method that pre-compensates the dephasing using three-dimensional selective excitation. The proposed 3DTRF pulses are designed iteratively with off-resonance incorporation and with a novel echo-volumar trajectory that frequency-encodes in z and phase-encodes in x,y . We also propose a computational scheme to accelerate the pulse design process. We demonstrate effective signal recovery in a 5-mm slice in both phantom and inferior brain, using 3DTRF pulses that are only 15.4 ms long. Compared to the original method, the new approach leads to significantly reduced pulse length and enhancement in slice selectivity. 3D images of the slice volume confirm fidelity of the excited phase pattern and slice profile. Magn Reson Med, 2006. © 2006 Wiley-Liss, Inc.