title: On T(2)-shortening by strongly magnetized spheres: a partial refocusing model.
abstract: Computer simulations of water transverse relaxation induced by superparamagnetic particles are shown to disagree with the available theories, covering the slow diffusion domain. Understanding these new simulations, not in the slow diffusion domain, thus requires a new theoretical approach. A "partial refocusing model" is introduced for this purpose; it is based on a spatial division between an inner region where the gradients are too strong for the refocusing pulses to be efficient and an outer region where they are efficient. This model agrees with published simulations of relaxation induced by magnetic dipoles approximated as points. The validity domains of the various models are also compared.
authors.affiliation: Biological Physics Department, Université de Mons Hainaut, B-7000 Mons, Belgium. pierre.gillis@umh.ac.be
authors.forename: Pierre
authors.initials: P
authors.lastname: Gillis
authors.forename: Francis
authors.initials: F
authors.lastname: Moiny
authors.forename: Rodney A
authors.initials: RA
authors.lastname: Brooks
mesh_terms: D003198:Computer Simulation; D004058:Diffusion; D017352:Echo-Planar Imaging; D005290:Ferric Compounds; D052203:Ferrosoferric Oxide; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008863:Microspheres; D008962:Models, Theoretical
chemical_list: D005290:Ferric Compounds; C427127:superparamagnetic blood pool agent; D052203:Ferrosoferric Oxide