title: Magnetic microparticle aggregation for viscosity determination by MR.
abstract: Micron-sized magnetic particles were induced to aggregate when placed in homogeneous magnetic fields, like those of MR imagers and relaxometers, and then spontaneously returned to their dispersed state when removed from the field. Associated with the aggregation and dispersion of the magnetic particles were time-dependent increases and decreases in the spin-spin relaxation time (T2) of the water. Magnetic nanoparticles, with far smaller magnetic moments per particle, did not undergo magnetically induced aggregation and exhibited time-independent values of T2. The rate of T2 change associated with magnetic microparticle aggregation was used to determine the viscosity of liquid samples, providing a method that can be of particular advantage for determining the viscosity of small volumes of potentially biohazardous samples of blood or blood plasma.
authors.affiliation: Center for Molecular Imaging Research, Harvard Medical School, Massachusetts General Hospital, Charlestown, Massachusetts 02129, USA.
authors.forename: Rui
authors.initials: R
authors.lastname: Hong
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Cima
authors.forename: Ralph
authors.initials: R
authors.lastname: Weissleder
authors.forename: Lee
authors.initials: L
authors.lastname: Josephson
mesh_terms: D003287:Contrast Media / Q000737:chemistry; D003911:Dextrans; D052203:Ferrosoferric Oxide / Q000737:chemistry; D007501:Iron / Q000737:chemistry*; D008279:Magnetic Resonance Imaging; D058185:Magnetite Nanoparticles; D053758:Nanoparticles / Q000737:chemistry*; D010087:Oxides / Q000737:chemistry*; D010316:Particle Size; D014783:Viscosity
chemical_list: D003287:Contrast Media; D003911:Dextrans; D058185:Magnetite Nanoparticles; D010087:Oxides; C499827:monocrystalline iron oxide nanoparticle; D007501:Iron; C065507:ferumoxides; D052203:Ferrosoferric Oxide