Suppression of background gradients in (B0 gradient-based) NMR diffusion experiments

Artifacts arising from background gradients are very common in NMR diffusion (i.e., PGSE) experiments involving B-0 gradients because of the unavoidable magnetic susceptibility differences and B-0 inhomogeneity within and around the sample. This article presents the general methodology to develop PGSE sequences with background gradient suppression. Most of the available methods which can be used for the suppression of the effects of background gradients are discussed. And two newly developed methods are presented in detail: frequency analysis of spin-clephasing, which assumes the artifacts due to background gradients come from the resonance between the spin-dephasing caused by applied gradients and background gradients, and asymmetric bipolar stimulated-echo-based PGSE, which can suppress the effects of nonconstant background gradients. (c) 2007 Wiley Periodicals, Inc.