Probing metabolite diffusion at ultra-short time scales in the mouse brain using optimized oscillating gradients and “short”-echo-time diffusion-weighted MRS
Abstract
Measuring diffusion at ultra‐short time scales may yield information about short‐range intracellu-lar structure and cytosol viscosity. However, reaching such time scales usually requires oscillatinggradients, which in turn imply long echo times T$_E$. Here we propose a new kind of stretchedoscillating gradient that allows us to increase diffusion‐weighting b while preserving spectraland temporal properties of the gradient modulation. We used these optimized gradients tomeasure 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 beobserved and used as an internal reference of approximately null diffusivity, which proved criticalto discard datasets corrupted by some motion artifact. The methods introduced here may beuseful to improve the accuracy and precision of metabolite apparent diffusion coefficientmeasurements with oscillating gradients.