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Published June 2002 | public
Journal Article

Repeated fMRI Using Iron Oxide Contrast Agent in Awake, Behaving Macaques at 3 Tesla


Iron oxide contrast agents have been employed extensively in anesthetized rodents to enhance fMRI sensitivity and to study the physiology of cerebral blood volume (CBV) in relation to blood oxygen level-dependent (BOLD) signal following neuronal activation. This study quantified the advantages of exogenous agent for repeated neuroimaging in awake, nonhuman primates using a clinical 3 Tesla scanner. A monocrystalline iron oxide nanoparticle (MION) solution was injected at iron doses of 8 to 10 mg/kg in two macaque monkeys. Adverse behavioral effects due to contrast agent were not observed in either monkey using cumulative doses in excess of 60 mg/kg. Relative to BOLD imaging at 3 Tesla, MION increased functional sensitivity by an average factor of 3 across the brain for a stimulus of long duration. Rapid stimulus presentation attenuated MION signal changes more than BOLD signal changes, due to the slower time constant of the blood volume response relative to BOLD signal. Overall, the contrast agent produced a dramatic improvement in functional brain imaging results in the awake, behaving primate at this field strength.

Additional Information

© 2002 Elsevier Science (USA) All rights reserved. Received October 8, 2001 The authors gratefully acknowledge financial support from the National Foundation for Functional Brain Imaging (U.S.A.), from the National Institutes of Health (J.B.M.: R01-RR14543A02; A.M.D.: R01-RR13609, P41-RR14075, R01-NS39581), from the Queen Elisabeth Medical Foundation (GSKE), and from the Flemish Regional Ministry of Education (G.A.O.: GOA 2000/11).

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