Heating in the MRI environment due to superparamagnetic fluid suspensions in a rotating magnetic field

JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS

卷:322

Article

Cantillon-Murphy, P.^1,2  Wald, L. L.³  Adalsteinsson, E.^2,3  Zahn, M.² 

[1] Brigham & Womens Hosp, Dept Gastroenterol, Boston, MA 02115 USA

[2] MIT, Dept Elect Engn & Comp Sci, Cambridge, MA 02139 USA

[3] MGH HSTAthinoula A Martinos Ctr Biomed Imaging, Charlestown, MA USA

关键词: Hyperthermia;    Magnetic nanoparticles;    MRI;    Heating;    Superparamagnetic fluid;   

DOI  :  10.1016/j.jmmm.2009.10.050

来源: Elsevier

【 摘 要 】

In the presence of alternating-sinusoidal or rotating magnetic fields, magnetic nanoparticles will act to realign their magnetic moment with the applied magnetic field. The realignment is characterized by the nanoparticle's time constant, tau. As the magnetic field frequency is increased, the nanoparticle's magnetic moment lags the applied magnetic field at a constant angle for a given frequency Omega, in rad/s. Associated with this misalignment is a power dissipation that increases the bulk magnetic fluid's temperature which has been utilized as a method of magnetic nanoparticle hyperthermia, particularly suited for cancer in low-perfusion tissue (e.g., breast) where temperature increases of between 4 and 7 degree Centigrade above the ambient in vivo temperature cause tumor hyperthermia. This work examines the rise in the magnetic fluid's temperature in the MRI environment which is characterized by a large DC field, B-0. Theoretical analysis and simulation is used to predict the effect of both alternating-sinusoidal and rotating magnetic fields transverse to B-0. Results are presented for the expected temperature increase in small tumors (approximately 1 cm radius) over an appropriate range of magnetic fluid concentrations (0.002-0.01 solid volume fraction) and nanoparticle radii (1-10 nm). The results indicate that significant heating can take place, even in low-field MRI systems where magnetic fluid saturation is not significant, with careful selection of the rotating or sinusoidal field parameters (field frequency and amplitude). The work indicates that it may be feasible to combine low-field MRI with a magnetic hyperthermia system using superparamagnetic iron oxide nanoparticles. (C) 2009 Elsevier B.V. All rights reserved.

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