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Probing metabolite diffusion at ultra‐short time scales in the mouse brain using optimized oscillating gradients and “short”‐echo‐time diffusion‐weighted MRS
Author(s) -
Ligneul Clémence,
Valette Julien
Publication year - 2017
Publication title -
nmr in biomedicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.278
H-Index - 114
eISSN - 1099-1492
pISSN - 0952-3480
DOI - 10.1002/nbm.3671
Subject(s) - diffusion , metabolite , signal (programming language) , thermal diffusivity , biological system , chemistry , nuclear magnetic resonance , physics , computer science , biology , thermodynamics , biochemistry , programming language
Measuring diffusion at ultra‐short time scales may yield information about short‐range intracellular structure and cytosol viscosity. However, reaching such time scales usually requires oscillating gradients, which in turn imply long echo times T E . Here we propose a new kind of stretched oscillating gradient that allows us to increase diffusion‐weighting b while preserving spectral and temporal properties of the gradient modulation. We used these optimized gradients to measure metabolite diffusion in the mouse brain down to effective diffusion times of 1 ms while keeping T E relatively short (60 ms). At such T E , a significant macromolecule signal could still be observed and used as an internal reference of approximately null diffusivity, which proved critical to discard datasets corrupted by some motion artifact. The methods introduced here may be useful to improve the accuracy and precision of metabolite apparent diffusion coefficient measurements with oscillating gradients.