Els Fieremans1, Dmitry S. Novikov1, Jens H. Jensen1, Joseph A. Helpern1,2
1Radiology, New York University School of Medicine, New York, United States; 2Center for Advanced Brain Imaging, Nathan S. Kline Institute, Orangeburg, NY, United States
Chemical exchange models have been frequently applied to quantify diffusion measurement in living tissues. Here we investigate numerically a two-compartment exchange (Krger) model as applied to diffusion in a system of parallel cylinders with permeable walls, which serves as a model for axons in white matter. We show that the Krger model accurately predicts the diffusivity and the diffusional kurtosis when the membranes are sufficiently impermeable. The exchange time can then be derived from the time-dependence of the diffusional kurtosis. For larger permeabilities, the Krger model overestimates the actual exchange time.