Brain ischemia.

The sensitivity of MRI to changes in water state and volume makes it the most desirable modality for imaging early brain ischemia. Its sensitivity is reflected in the ability to show ischemic changes in the white matter of the asymptomatic elderly, which are attributed to axonal loss, demyelination, and gliosis. In large infarcts, however, contrast enhancement with Gd-DTPA can be used to add specificity, should doubt exist as to the proper diagnosis. The ability of MR to image flow is a valuable adjunct, and MR angiography has the potential partially to replace invasive angiography. Applications of MR such as diffusion-perfusion studies, sodium imaging, and spectroscopy could all prove to be useful in the future.