Abstract #4915

Assessment of two T1D components within myelinated tissue with ihMT MRI

Victor N. D. Carvalho^1,2, Olivier M. Girard¹, Andreea Hertanu¹, Samira Mchinda¹, Lucas Soustelle¹, Axelle Grélard³, Antoine Loquet³, Erick J. Dufourc³, Gopal Varma⁴, David C. Alsop⁴, Pierre Thureau², and Guillaume Duhamel¹

¹Aix Marseille Univ, CNRS, CRMBM UMR 7339, Marseille, France, ²Aix Marseille Univ, CNRS, ICR UMR 7273, Marseille, France, ³CBMN UMR 5248, CNRS University of Bordeaux, Pessac, France, ⁴Department of Radiology, Division of MR Research, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, United States

T_1D, the relaxation time of the dipolar order, is a probe for membrane dynamics and organization that could be used to assess myelin integrity. A single-component T_1D model associated with a modified ihMT sequence had been proposed for in vivo evaluation of T_1D with MRI. However, experiments and simulations revealed that myelinated tissues exhibit multiple T_1D components. A bi-component T_1Dmodel is proposed and validated. Fits in a rat spinal cord yield two T_1Ds of about 10 ms and 400 μs. The results suggest that myelin has a dynamically heterogeneous organization.

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