The Major Fraction of Intracellular Metabolites in the Primate Brain Is Localized in Long Fibers Rather Than in Cell Bodies, as Shown by Diffusion-Weighted Spectroscopy at Long & Ultra-Long Diffusion Times

Chlo Najac¹, ², Charlotte Marchadour¹, ², Martine Guillermier¹, ², Philippe Hantraye¹, ², Vincent Lebon¹, ², Julien Valette¹, ²

In Vivo diffusion-weighted spectroscopy offers unique insights into cell architecture. At long diffusion times td, the geometry of the compartment where diffusion occurs deeply affects the apparent diffusion coefficient (ADC). In the present study, we investigated brain metabolites ADC variation at long and ultra-long td (up to 1 second). No strong dependence of NAA, creatine and choline ADC on td was observed over the large time-window. Data modeling using geometrically constrained diffusion models leads to the conclusion that a major fraction of brain metabolites diffuse in long fibers such as axons and dendrites.