Measuring SPIO and Gd contrast agent magnetization using 3T MRI
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Zahn_Measuring SPIO.pdf
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Author(s)
Cantillon-Murphy, Padraig
Wald, Lawrence L.
Zahn, Markus
Adalsteinsson, Elfar
Date Issued
May 2009
Journal
NMR in Biomedicine
Publisher
John Wiley & Sons, Ltd.
Citation
Cantillon-Murphy, Padraig, Lawrence L. Wald, and Markus Zahn. “Measuring SPIO and Gd contrast agent magnetization using 3T MRI.” NMR in Biomedicine 22.8 (2009): 891-897.
Version
Author's final manuscript
Abstract
Traditional methods of measuring magnetization in magnetic fluid samples, such as vibrating sample magnetometry (VSM), are typically limited to maximum field strengths of about 1 T. This work demonstrates the ability of MRI to measure the magnetization associated with two commercial MRI contrast agents at 3 T by comparing analytical solutions to experimental imaging results for the field pattern associated with agents in cylindrical vials. The results of the VSM and fitted MRI data match closely. The method represents an improvement over VSM measurements since results are attainable at imaging field strengths. The agents investigated are Feridex, a superparamagnetic iron oxide suspension used primarily for liver imaging, and Magnevist, a paramagnetic, gadolinium-based compound used for tumors, inflammation and vascular lesions. MR imaging of the agents took place in sealed cylindrical vials in the presence of a surrounding volume of deionized water where the effects of the contrast agents had a measurable effect on the water's magnetization in the vicinity of the compartment of contrast agent. A pair of phase images were used to reconstruct a B0 fieldmap. The resultant B0 maps in the water region, corrected for shimming and container edge effects, were used to predict the agent's magnetization at 3 T. The results were compared with the results from VSM measurements up to 1.2 T and close correlation was observed. The technique should be of interest to those seeking quantification of the magnetization associated with magnetic suspensions beyond the traditional scope of VSM. The magnetization needs to be sufficiently strong (Ms 50 Am2/kg Fe for Feridex and Xm 5 × 10-5 m3/kg Gd for Magnevist) for a measurable dipole field in the surrounding water. For this reason, the technique is mostly suitable for undiluted agents.
Subjects
dipole field
contrast agents
magnetization
MRI
Magnevist
vibrating sample magnetometry
Feridex
MIT Department
Harvard University--MIT Division of Health Sciences and Technology
Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science
Massachusetts Institute of Technology. Research Laboratory of Electronics
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DOI of Published Version
https://doi.org/10.1002/nbm.1412
