Diffusion and perfusion MRI: basic physics

Diffusion and perfusion MR imaging are now being used increasingly in neuro -vascular clinical applications. While diffusion weighted magnetic resonanc e imaging exploits the translational mobility or water molecules to obtain information on the microscopic behavioral of the tissues (presence of macro molecules, presence and permeability of membranes, equilibrium intracellula r-extracellular water....). perfusion weighted imaging makes use of endogen ous and exogenous tracers for monitoring their hemodynamic status. The comb ination of both techniques is extremely promising for the early detection a nd assessment of stroke, for tumor characterisation and for the evaluation of neurogenerative diseases. This article provides a brief review of the ba sic physics principles underlying the methodologies followed. (C) 2001 Else vier Science Ireland Ltd. All rights reserved.