Scaling of transverse nuclear magnetic relaxation due to magnetic nanoparticle aggregation
Name
Cima_Scaling of transverse.pdf
Size
882.1 KB
Format
Adobe PDF
Checksum (MD5)
a855bf302e1bf19ef66fbf2a90e53a39
Author(s)
Brown, Keith A.
Vassiliou, Christophoros C.
Issadore, David
Berezovsky, Jesse
Cima, Michael J.
Westervelt, R.M.
Date Issued
May 2010
Journal
Journal of Magnetism and Magnetic Materials
Publisher
Elsevier
Citation
Brown, Keith A., Christophoros C. Vassiliou, David Issadore, Jesse Berezovsky, Michael J. Cima, and R.M. Westervelt. “Scaling of Transverse Nuclear Magnetic Relaxation Due to Magnetic Nanoparticle Aggregation.” Journal of Magnetism and Magnetic Materials 322, no. 20 (October 2010): 3122–3126.
Version
Author's final manuscript
Abstract
The aggregation of superparamagnetic iron oxide (SPIO) nanoparticles decreases the transverse nuclear magnetic resonance (NMR) relaxation time T[CP over 2] of adjacent water molecules measured by a Carr-Purcell-Meiboom-Gill (CPMG) pulse-echo sequence. This effect is commonly used to measure the concentrations of a variety of small molecules. We perform extensive Monte Carlo simulations of water diffusing around SPIO nanoparticle aggregates to determine the relationship between T[CP over 2] and details of the aggregate. We find that in the motional averaging regime T[CP over 2] scales as a power law with the number N of nanoparticles in an aggregate. The specific scaling is dependent on the fractal dimension d of the aggregates. We find T[CP over 2] ∝ Ν[superscript −0.44] for aggregates with d = 2.2, a value typical of diffusion limited aggregation. We also find that in two-nanoparticle systems, T[CP over 2] is strongly dependent on the orientation of the two nanoparticles relative to the external magnetic field, which implies that it may be possible to sense the orientation of a two-nanoparticle aggregate. To optimize the sensitivity of SPIO nanoparticle sensors, we propose that it is best to have aggregates with few nanoparticles, close together, measured with long pulse-echo times.
MIT Department
Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science
Massachusetts Institute of Technology. Department of Materials Science and Engineering
Koch Institute for Integrative Cancer Research at MIT
Terms of Use
Creative Commons Attribution-Noncommercial-NoDerivatives
Persistent DSpace Link
DOI of Published Version
https://doi.org/10.1016/j.jmmm.2010.05.044
