Multiple gradient echo sequence optimized for rapid, single-scan mapping of R(2)(*) at high B0.
A multiple-gradient-echo sequence is proposed for accurately mapping R(2)(*) in the presence of in-slice macroscopic susceptibility gradients. In-slice signal loss caused by background macroscopic susceptibility gradients is mitigated by combining three successive gradient-echo images whose slice refocus gradients are successively incremented. The optimum incrementation of slice-refocusing gradients was determined by numerical simulation. By repeating further cycles of three images in the same sequence, artifact-compensated data spanning a range of echo times (TEs) was acquired leading to single-scan, R(2) (*) maps that are quantitatively reflective of microscopic field inhomogeneities. The performance of the sequence was demonstrated at 3.0T, first with a doped aqueous phantom, and then on the head of a normal volunteer. That performance is compared quantitatively with previously published work.
Wild
Jim M
JM
Department of Biomedical Engineering, University of Alberta, Edmonton, Canada. j.m.wild@sheffield.ac.uk
Martin
W R Wayne
WR
Allen
Peter S
PS
D016477:Artifacts; D001921:Brain / Q000033:anatomy & histology*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*