Improved neuronal tract tracing using manganese enhanced magnetic resonance imaging with fast T1 mapping

Authors

  • Kai-Hsiang Chuang,

    1. Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, NIH, Bethesda, Maryland, USA
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  • Alan Koretsky

    Corresponding author
    1. Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, NIH, Bethesda, Maryland, USA
    • Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, 10 Center Drive, 10/B1D728, Bethesda, MD 20892-1065, USA
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  • This article is a US Government work and, as such, is in the public domain in the United States of America.

Abstract

There has been growing interest in using manganese-enhanced MRI (MEMRI) to detect neuronal activation, neural architecture, and neuronal connections. Usually Mn2+ produces a very wide range of T1 change. In particular, in neuronal tract tracing experiments the site of Mn2+ injection can have very short T1 while distant regions have small T1 reductions, primarily due to dilution of Mn2+. Most MEMRI studies use T1-weighted sequences, which can only give optimal contrast for a narrow range of T1 changes. To improve sensitivity to the full extent of Mn2+ concentrations and to optimize detection of low concentrations of Mn2+, a fast T1 mapping sequence based on the Look and Locker technique was implemented. Phantom studies demonstrated less than 6.5% error in T1 compared to more conventional T1 measurements. Using center-out segmented EPI, whole-brain 3D T1 maps with 200-μm isotropic resolution were obtained in 2 h from rat brain. Mn2+ transport from the rat olfactory bulb through appropriate brain structures could be detected to the amygdala in individual animals. The method reliably detected less than 7% reductions in T1. With this quantitative imaging it should be possible to study more extensive pathways using MEMRI and decrease the dose of Mn2+ used. Magn Reson Med, 2006. Published 2006 Wiley-Liss, Inc.

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