Diffusion anisotropy in excised normal rat spinal cord measured by NMR microscopy |
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| Institution: | 1. Center for Structural Biology, Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, FL, USA;2. Department of Physics, University of Florida, Gainesville, FL, USA;3. Department of Neuroscience, University of Florida, Gainesville, FL, USA;1. University of Ottawa, Neuroscience Graduate Program, 451 Smyth Road, Ottawa, ON, Canada K1H 8M5;2. Ottawa Hospital Research Institute, Neuroscience, 451 Smyth Road, Ottawa, ON, Canada K1H 8M5;1. Univ. Lille and Artois, ENSCL, Centrale Lille, UCCS, CNRS UMR 8181, 59000, Lille, France;2. Bruker France, 34 rue de l’Industrie, 67166, Wissembourg, France;3. IUF, Institut Universitaire de France, 75231, Paris, France;1. Bridge12 Technologies, 37 Loring Drive, Framingham, MA 01702, USA;2. Institute for Molecules and Materials, Radboud University, Nijmegen, The Netherlands;1. NMR Science and Development Division, RIKEN SPring-8 Center, and Nano-Crystallography Unit, RIKEN-JEOL Collaboration Center, Yokohama, Kanagawa 230-0045, Japan;2. TIFR Centre for Interdisciplinary Sciences, Tata Institute of Fundamental Research Hyderabad, Sy. No. 36/P, Gopanpally, Ranga Reddy District, Hyderabad 500 107, India;3. JEOL RESONANCE Inc., Musashino, Akishima, Tokyo 196-8558, Japan;1. 1st Department of Neurology, School of Medicine, National & Kapodistrian University of Athens, Athens, Greece;2. Department of Radiology, Therapeutic Center of Athens ‘‘Lefkos Stavros’’, Athens, Greece;3. Montreal Neurological Institute and Hospital, McGill University, Montreal, Quebec, Canada |
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| Abstract: | A conventional spin-echo NMR imaging pulse sequence was used to obtain high-resolution images of excised normal rat spinal cord at 7 and 14 T. It was observed that the large pulsed-field gradients necessary for high-resolution imaging caused a diffusion weighting that dominated the image contrast and that could be used to infer microscopic structural organization beyond that defined by the resolution of the image matrix (i.e., fiber orientation could be assigned based on diffusion anisotropy). Anisotropic diffusion coefficients were therefore measured using apparent diffusion tensor (ADT) imaging to assess more accurately fiber orientations in the spinal cord; structural anisotropy information is portrayed in the six unique images of the complete ADT. To reduce the dimensionality of the data, a trace image was generated using a separate color scale for each of the three diagonal element images of the ADT. This new image retains much of the invariance of the trace to the relative orientations of laboratory and sample axes (inherent to a greyscale trace image) but provides, by the use of color, contrast reflecting diffusion anisotropy. The colored trace image yields a pseudo-three-dimensional view of the rat spinal cord, from which it is possible to deduce fiber orientations. |
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