MR DIFFUSION IMAGING IN STROKE - REVIEW AND CONTROVERSIES

Magnetic resonance (MR) diffusion imaging allows detection of cerebral ischemia within minutes of onset, and the temporal evolution of diffu sion characteristics enables differentiation of acute from chronic str oke. T2-weighted MR imaging demonstrates infarcted tissue but fails to demonstrate acutely ischemic regions. Furthermore, the similar signal intensity characteristics of acute and chronic stroke on T2-weighted images Limit the ability to determine the acuteness of an infarct, Dif fusion imaging thus has tremendous potential for helping direct the tr eatment of acute ischemic stroke. Controversy exists over the pathophy siology of underlying changes in diffusion and the reversibility of ch anges after reperfusion in humans. There is also a lack of reproducibi lity in the time course of diffusion changes between research centers. Use of optimal diffusion imaging strategies results in increased cons picuity of ischemic regions and increased reproducibility of diffusion constants between research centers. An understanding of the principle s of diffusion imaging and current controversies in the field is neces sary for optimal application of this technique in the evaluation and t reatment of cerebral ischemia.