DIFFUSION-WEIGHTED NMR IMAGING - APPLICATION TO EXPERIMENTAL FOCAL CEREBRAL-ISCHEMIA

Changes in diffusion MMR imaging are believed to be based on intra/ext racellular water homeostasis and will therefore reflect early disturba nces of ion and water homeostasis after the onset of an ischemic event , Diffusion-weighted NMR imaging (DWI) thus has the potential to be a sensitive tool for the observation of stroke evolution. The present st ate of information extracted from diffusion-weighted NMR imaging for t he understanding of cerebral focal ischemia in experimental research h as been compiled in this review, The emphasis was set on three essenti al aspects of the technique in relation to focal ischemia, Firstly, th e sensitivity of diffusion-weighted imaging for ischemic alterations i s described, A comparison with conventional NMR imaging using relaxati on time changes is included. Secondly, the comparison of the diffusion -weighted imaging with invasive techniques is discussed, Here, interpr etation of the physiological, metabolic and hemodynamic alterations re flected in the observed diffusion changes is presented, The importance of regionally resolved information for a meaningful assignment of DWI changes to pathophysiological alterations is demonstrated for the dif ferentiation between ischemic core and penumbra from DWI and quantitat ive diffusion coefficient data. The time dependence of correlations wi th physiological, biochemical and hemodynamic variables as a further i mportant aspect is stressed, Thirdly, the potential of the technique f or the assessment of development and effectiveness of new therapeutica l strategies against stroke is demonstrated.