Abstract
Diffusion-weighted imaging (DWI) using magnetic resonance imaging (MRI) reflects the influence of the intra- and extracellular diffusion coefficient of water and cell membrane permeability. Previous diffusion MRI studies have focused mainly on measurement of the effective diffusion coefficient of water molecules in biological tissues, but details of the underlying microscopic structures were not clear. Various models have been proposed for clarifying the relation between diffusion MRI signals and diffusion properties in cells, and numerical simulation of water diffusion provides a useful tool for estimation of cellular variables. The purpose of this study is to evaluate the influence of cellular variables on diffusion MRI signals and to estimate intracellular diffusion coefficient and cell membrane permeability of the normal rat and human brain. By minimizing the difference between signals obtained experimentally and those from numerical simulation, we could estimate intracellular diffusion coefficient (rat: (0.9±0.4) ×10-3mm2/s, human: (1.2±0.2) ×10-3mm2/s) and membrane permeability (rat: 68±6 μm/s, human: 80±13 μm/s). Our method is useful for non-invasively estimating the cell membrane permeability of biological tissues, and is easily applicable to human tissues and other samples.
