Neurite Exchange Imaging (NEXI): A minimal model of diffusion in gray matter with inter-compartment water exchange

Biophysical models of diffusion in white matter are based on what is now commonly referred to as the "Standard Model" (SM) of non-exchanging anisotropic Gaussian compartments. In this work, we focus on diffusion MRI in gray matter, which requires rethinking basic microstructure modeling blocks. In particular, at least three contributions beyond the SM need to be considered: water exchange across the cell membrane - between neurites and the...