Magnetic resonance imaging of diffusion and perfusion.

Two promising advances in MRI have recently evolved. Water proton directional "diffusion" as well as "perfusion" processes can be imaged in a rapid (on the order of milliseconds) and accurate manner. MR diffusion imaging is shown to effectively allow determination of the presence of anisotropic water diffusion in animal and human cerebral and spinal white matter and in peripheral nerves. In another important application, the measured apparent water proton diffusion is observed to be significantly slowed in cerebral gray matter within the first minutes following experimental stroke suggesting that MRI could be useful in rapid initial assessments of ischemic damage. MR contrast media can cause regional changes due to either magnetic susceptibility-induced T2* shortening or to paramagnetic-induced T1 shortening. The passage of a contrast bolus through the microcirculation can be monitored using high-speed MRI and can provide significant contrast enhancement in ischemic and normally perfused tissues.