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Enhancement and degradation of the R 2 * relaxation rate resulting from the encapsulation of magnetic particles with hydrophilic coatings
Author(s) -
de Haan Hendrick W.,
Paquet Chantal
Publication year - 2011
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.22944
Subject(s) - dephasing , coating , materials science , scaling , particle size , relaxation (psychology) , monte carlo method , particle (ecology) , diffusion , range (aeronautics) , chemical physics , condensed matter physics , nanotechnology , chemistry , physics , thermodynamics , composite material , psychology , social psychology , geometry , mathematics , statistics , oceanography , geology
The effects of including a hydrophilic coating around the particles are studied across a wide range of particle sizes by performing Monte Carlo simulations of protons diffusing through a system of magnetic particles. A physically realistic methodology of implementing the coating by cross boundary jump scaling and transition probabilities at the coating surface is developed. Using this formulation, the coating has three distinct impacts on the relaxation rate: an enhancement at small particle sizes, a degradation at intermediate particle sizes, and no effect at large particles sizes. These varied effects are reconciled with the underlying dephasing mechanisms by using the concept of a full dephasing zone to present a physical picture of the dephasing process with and without the coating for all sizes. The enhancement at small particle sizes is studied systemically to demonstrate the existence of an optimal ratio of diffusion coefficients inside/outside the coating to achieve maximal increase in the relaxation rate. Magn Reson Med, 2011. © 2011 Wiley Periodicals, Inc.