Early detection of regional cerebral ischemia using high-speed MRI.

Background and Purpose: Diffusion-weighted magnetic resonance imaging (MRI) has been shown to be effective in detailing regions of cerebral ischemia in which water proton translations or motions have been slowed. The corresponding perfusion patterns, however, have not been correlated. Further, the hemodynamics of normal and ischemic tissues and the changes due to mild insults are also not clear. This study describes high-speed MRI techniques and observations found in the early detection of regional cerebral ischemia in the cat.
Methods: Gradient-echo and spin-echo-planar MRI was used with middle cerebral artery balloon occluders to induce transient ischemia and reperfusion.
Results: Apparent diffusion fell within minutes after middle cerebral artery occlusion and correlated with near-total or total perfusion deficits. Reactive hyperemia, apnea, and vasodilatation appeared to be changed in ischemic and normal brain.
Conclusions: Characterization of early ischemic events is dramatically improved when the motions of water (apparent diffusion), delivery of water (perfusion), and response to hemodynamic perturbations (regulatory response) are measured. All can be accomplished with high-speed MRI techniques described herein.