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Early detection of regional cerebral ischemia using high-speed MRI
M E Moseley1, A J de Crespigny, T P Roberts
1Department of Radiology, University of California, San Francisco 94143.
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.
Insights
High-speed magnetic resonance imaging (MRI) detects early cerebral ischemia by measuring water diffusion and perfusion. This technique correlates diffusion changes with blood flow deficits, aiding in understanding brain injury.
Area of Science:
- Neuroimaging
- Medical Physics
- Cerebrovascular Research
Background:
- Diffusion-weighted MRI effectively identifies cerebral ischemia by detecting slowed water proton motion.
- Correlation of perfusion patterns with diffusion changes in ischemia is not well-established.
- Hemodynamics in normal and ischemic brain tissues, and responses to mild insults, require further clarification.
Purpose of the Study:
- To describe high-speed MRI techniques for early detection of regional cerebral ischemia.
- To correlate diffusion patterns with perfusion deficits in ischemic brain.
- To investigate hemodynamic changes in normal and ischemic brain tissue.
Main Methods:
- Gradient-echo and spin-echo-planar MRI were employed.
- Transient ischemia and reperfusion were induced using middle cerebral artery balloon occluders in cats.
Main Results:
- Apparent diffusion decreased within minutes of middle cerebral artery occlusion.
- Reduced diffusion correlated with near-total or total perfusion deficits.
- Ischemic and normal brain exhibited altered reactive hyperemia, apnea, and vasodilatation.
Conclusions:
- High-speed MRI enables simultaneous measurement of water motion (apparent diffusion) and delivery (perfusion).
- Integrating diffusion, perfusion, and hemodynamic response characterization significantly improves early ischemic event detection.
- These comprehensive measurements can be achieved using the described high-speed MRI techniques.