title: Structure-specific magnetic field inhomogeneities and its effect on the correlation time.
abstract: We describe the relationship between the correlation time and microscopic spatial inhomogeneities in the static magnetic field. The theory takes into account diffusion of nuclear spins in the inhomogeneous field created by magnetized objects. A simple general expression for the correlation time is obtained. It is shown that the correlation time is dependent on a characteristic length, the diffusion coefficient of surrounding medium, the permeability of the surface and the volume fraction of the magnetized objects. For specific geometries (spheres and cylinders), exact analytical expressions for the correlation time are given. The theory can be applied to contrast agents (magnetically labeled cells), capillary network, BOLD effect and so forth.
authors.affiliation: Bayerische Julius-Maximilians-Universität Würzburg, Lehrstuhl für Experimentelle Physik 5, 97074 Würzburg, Germany. ziener@physik.uni-wuerzburg.de
authors.forename: Christian H
authors.initials: CH
authors.lastname: Ziener
authors.forename: Wolfgang R
authors.initials: WR
authors.lastname: Bauer
authors.forename: Gerd
authors.initials: G
authors.lastname: Melkus
authors.forename: Thomas
authors.initials: T
authors.lastname: Weber
authors.forename: Volker
authors.initials: V
authors.lastname: Herold
authors.forename: Peter M
authors.initials: PM
authors.lastname: Jakob
mesh_terms: D008279:Magnetic Resonance Imaging; D008280:Magnetics; D008433:Mathematics; D008962:Models, Theoretical