New Insight into the Contrast in Diffusional Kurtosis Images: Does It Depend on Magnetic Susceptibility?

PurposeIn this MRI study, diffusional kurtosis imaging (DKI) and T-2* multiecho relaxometry were measured from the white matter (WM) of human brains and correlated with each other, with the aim of investigating the influence of magnetic-susceptibility ((H2O-TISSUE)) on the contrast. MethodsWe focused our in vivo analysis on assessing the dependence of mean, axial, and radial kurtosis (MK, K, K), as well as DTI indices on (H2O-TISSUE) (quantified by T-2*) between extracellular water and WM tissue molecules. Moreover, Monte Carlo (MC) simulations were used to elucidate experimental data. ResultsA significant positive correlation was observed between K-perpendicular to, MK and R-2*=1/T-2*, suggesting that (H2O-TISSUE) could be a source of DKI contrast. In this view, K-perpendicular to and MK-map contrasts in human WM would not just be due to different restricted diffusion processes of compartmentalized water but also to local (H2O-TISSUE). However, MC simulations show a strong dependence on microstructure rearrangement and a feeble dependence on (H2O-TISSUE) of DKI signal. ConclusionOur results suggests a concomitant and complementary existence of multi-compartmentalized diffusion process and (H2O-TISSUE) in DKI contrast that might explain why kurtosis contrast is more sensitive than DTI in discriminating between different tissues. However, more realistic numerical simulations are needed to confirm this statement. Magn Reson Med 73:2015-2024, 2015. (c) 2014 Wiley Periodicals, Inc.