Numerical studies of intermolecular multiple quantum coherences: High-resolution NMR in inhomogeneous fields and contrast enhancement in MRI

A fast, efficient numerical algorithm is used to study intermolecular zero-quantum coherences (iZQCs) and double-quantum coherences (iDQCs) in two applications where the three-dimensional structure of the magnetization is important: high-resolution NMR in inhomogeneous fields and contrast enhancement in MRI. Simulations with up to 2 million coupled volume elements (256 x 256 x 32) show that iZQCs can significantly narrow linewidths in the indirectly detected dimension of systems with inhomogeneous fields and explore the effects of shape and orientation of the inhomogeneities. In addition, this study shows that MR images from iZQC and iDQC CRAZED pulse sequences contain fundamentally new contrast, and a modified CRAZED pulse sequence (modCRAZED) can isolate the contrast from chemically inequivalent spins. (C) 2000 Academic Press.