k‐TE generalized autocalibrating partially parallel acquisition (GRAPPA) for accelerated multiple gradient‐recalled echo (MGRE) R2* mapping in the abdomen

Multiple gradient‐recalled echo (MGRE) methods are commonly used for abdominal R₂* mapping. Accelerated MGRE acquisitions would offer the potential to shorten requisite breathhold times and/or increase spatial resolution and coverage. In both phantom and normal volunteer studies, view‐sharing (VS) methods, generalized autocalibrating partially parallel acquisition (GRAPPA) methods, and newly proposed k–echo time (k‐TE) GRAPPA methods were compared for the purpose of accelerating MGRE acquisitions. Utilization of water‐selective spatial spectral excitation pulses reduced artifact levels for both VS and k‐TE GRAPPA approaches. VS approaches were found to be highly sensitive to off‐resonance effects, particularly at increasing acceleration rates. k‐TE GRAPPA significantly reduced residual artifact levels compared to GRAPPA approaches while improving the accuracy of accelerated abdominal R₂* measurements. These initial feasibility studies demonstrate that k‐TE GRAPPA is an effective method to reduce scan times during abdominal R₂*‐mapping procedures. Magn Reson Med, 2009. © 2008 Wiley‐Liss, Inc.