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Diffusion-weighted MRI for evaluation of acute stroke
1Department of Neurology and Neurological Sciences and the Stanford Stroke Center, Stanford University Medical Center, CA 94304, USA.
Abstract:
Diffusion-weighted imaging (DWI) is a new magnetic resonance imaging technique that detects the tiny random movements of water molecules (diffusion) in tissues. This technique allows a map of the average apparent diffusion coefficient (ADC) to be calculated. Shortly after the onset of an ischemic stroke, the ADC of brain tissue is significantly reduced because of cytotoxic edema. Over several days, the rapid initial drop in ADC is followed by a return to "pseudonormal" values at approximately 1 week. Subsequently, elevated ADC values are seen at chronic time points. DWI is remarkably sensitive in detecting and localizing acute ischemic brain lesions and allows differentiation of acute regions of ischemia from chronic infarcts. Recent studies have shown a high correlation between the volume of early DWI lesions and clinical neurologic outcome. In addition, the volume of the early DWI lesion correlates well with final infarct volume as measured by T2-weighted imaging. Therefore, this technique may facilitate optimal selection of patients for new medical therapies for stroke and may provide a highly sensitive technique for evaluating the efficacy of new treatments.
Insights
Diffusion-weighted imaging (DWI) detects changes in apparent diffusion coefficient (ADC) in ischemic stroke. This MRI technique aids in early lesion detection, outcome prediction, and treatment evaluation.
Area of Science:
- Neurology
- Radiology
- Medical Imaging
Background:
- Diffusion-weighted imaging (DWI) is an advanced MRI technique.
- It measures water molecule diffusion to calculate the apparent diffusion coefficient (ADC) map.
- Acute ischemic stroke causes cytotoxic edema, significantly reducing ADC values.
Purpose of the Study:
- To evaluate the utility of DWI in detecting and characterizing ischemic stroke.
- To assess the correlation between DWI lesion volume and clinical outcomes.
- To determine DWI's potential in patient selection for stroke therapies and treatment efficacy evaluation.
Main Methods:
- Utilizing diffusion-weighted imaging (DWI) to assess brain tissue.
- Calculating apparent diffusion coefficient (ADC) maps.
- Analyzing ADC value changes over time post-stroke onset.
Main Results:
- ADC values decrease acutely post-ischemic stroke due to cytotoxic edema.
- ADC values return to pseudonormal levels around 1 week, then elevate chronically.
- Early DWI lesions show high correlation with clinical neurologic outcome and final infarct volume.
Conclusions:
- DWI is highly sensitive for detecting and localizing acute ischemic brain lesions.
- It effectively differentiates acute from chronic infarcts.
- DWI facilitates patient selection for stroke therapies and aids in evaluating treatment efficacy.