title: Scaling laws for transverse relaxation times.
abstract: Simple scaling laws are useful tools in understanding the effect of changing parameters in MRI experiments. In this paper the general scaling behavior of the transverse relaxation times is discussed. We consider the dephasing of spins diffusing around a field inhomogeneity inside a voxel. The strong collision approximation is used to describe the diffusion process. The obtained scaling laws are valid over the whole dynamic range from motional narrowing to static dephasing. The dependence of the relaxation times on the external magnetic field, diffusion coefficients of the surrounding medium, and the characteristic scale of the field inhomogeneity is analyzed. For illustration the generally valid scaling laws are applied to the special case of a capillary, usually used as a model of the myocardial BOLD effect.
authors.affiliation: Bayerische Julius-Maximilians-Universität Würzburg, Institut für Experimentelle Physik 5, Am Hubland, 97074 Würzburg, Germany. ziener@physik.uni-wuerzburg.de
authors.forename: C H
authors.initials: CH
authors.lastname: Ziener
authors.forename: T
authors.initials: T
authors.lastname: Kampf
authors.forename: G
authors.initials: G
authors.lastname: Melkus
authors.forename: P M
authors.initials: PM
authors.lastname: Jakob
authors.forename: W R
authors.initials: WR
authors.lastname: Bauer
mesh_terms: D000465:Algorithms; D003198:Computer Simulation; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008954:Models, Biological; D013997:Time Factors