|Title||In vivo observation and biophysical interpretation of time-dependent diffusion in human white matter.|
|Publication Type||Journal Article|
|Year of Publication||2016|
|Authors||Fieremans, E, Burcaw, LM, Lee, H-H, Lemberskiy, G, Veraart, J, Novikov, DS|
The presence of micrometer-level restrictions leads to a decrease of diffusion coefficient with diffusion time. Here we investigate this effect in human white matter in vivo. We focus on a broad range of diffusion times, up to 600ms, covering diffusion length scales up to about 30 μm. We perform stimulated echo diffusion tensor imaging on 5 healthy volunteers and observe a relatively weak time-dependence in diffusion transverse to major fiber tracts. Remarkably, we also find notable time-dependence in the longitudinal direction. Comparing models of diffusion in ordered, confined and disordered media, we argue that the time-dependence in both directions can arise due to structural disorder, such as axonal beads in the longitudinal direction, and the random packing geometry of fibers within a bundle in the transverse direction. These time-dependent effects extend beyond a simple picture of Gaussian compartments, and may lead to novel markers that are specific to neuronal fiber geometry at the micrometer scale.
|Grant List||P30 AG008051 / AG / NIA NIH HHS / United States |
R01 NS088040 / NS / NINDS NIH HHS / United States
bridging the micro-macro gap with diffusion MRI