Investigation of the time- and frequency-dependence of diffusion kurtosis in the human brain with pulsed and oscillating gradient experiments

Motivation: Investigation of the time- and frequency-dependence of diffusion kurtosis, a valuable probe of microstructure and exchange, is becoming feasible in humans due to advances of gradient hardware. Goal(s): To provide more data regarding time- and frequency-dependent diffusion kurtosis in the human brain. Approach: Diffusion MRI with pulsed and oscillating gradients (PGSE/OGSE) at different but partially overlapping diffusion times using a head gradient insert and spiral readouts. Results: Biphasic kurtosis behavior (i.e., increase with time in the short-time range and decrease with time in the long-time range covered by OGSE/PGSE, respectively) was observed, with an explainable mismatch between both sequences in the overlapping range. Impact: Studying the time- and frequency-dependence of diffusion kurtosis using both PGSE and OGSE experiments over a range of diffusion times and length scales can provide valuable information about brain tissue complexity, heterogeneity, and inter-compartmental water exchange.