Intra- and extra-axonal axial diffusivities in the white matter: which one is faster?

摘要: A two-compartment model of diffusion in white matter, which accounts for intra- and extra-axonal spaces, is associated with two plausible mathematical scenarios: either the intra-axonal axial diffusivity higher than (Branch 1), or opposite 2). This duality calls an independent validation compartment diffusivities, to determine cases holds. The aim present study was use intracerebroventricular injection a gadolinium-based contrast agent selectively reduce extracellular water signal rat brain, compare metrics genu corpus callosum before after gadolinium infusion. considered were kurtosis tensor metrics, as well compartment-specific estimates WMTI-Watson model. strong decrease T1 T2 relaxation times post-Gd observed (p < 0.001), increase 48% radial 0.05), implies that relative fraction decreased. further supported by significant estimated from model, both branches 0.01 Branch 1, p 0.05 However, pre-Gd axon dispersion 1 agreed better literature those 2. Furthermore, comparison changes between data simulations biologically solution, i.e. one. result fully consistent other recent measurements diffusivities used entirely different approaches, such encoding.