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Correlation of apparent diffusion coefficient and computed tomography density in acute ischemic stroke
Thomas Kucinski1, Ole Väterlein, Volkmar Glauche
1Department of Neuroradiology, University-Hospital Hamburg Eppendorf, Hamburg, Germany. kucinski@ uke.uni-hanburg.de
Background And Purpose:
Diffusion-weighted MR imaging is very sensitive for the detection of restricted molecular water diffusion in acute ischemic stroke. CT is sensitive to net water uptake in ischemic edema. We compared the decrease in the apparent diffusion coefficient (ADC) in diffusion-weighted MR imaging with CT density changes to study the correlation between diffusion restriction and water uptake in acute stroke patients.
Methods:
Twenty-five patients with acute ischemic stroke of the anterior cerebral circulation underwent MR and CT imaging 1.3 to 5.4 hours after symptom onset. ADC and CT data were transferred into a common 3-dimensional space, and regions of decreased ADC (dADC) were superimposed onto the corresponding CT. Mean values of ADC and Hounsfield units (HU) were determined in comparison with the nonaffected hemisphere.
Results:
Mean decrease in ADC (dADC) was 170+/-53x 10(-6) mm2/s and corresponded to a decrease (dCT) in CT density of 1.3+/-0.7 HU. dCT showed a continuous linear decrease of 0.4 HU/h (r=0.55, P<0.01), whereas the decrease is ADC was almost complete after 1.5 hours. A correlation between the decrease in ADC and dCT was found (r=0.41, P=0.04).
Conclusions:
The severity of diffusion restriction correlates with net water uptake in acute ischemic stroke. However, the underlying pathophysiology and different time courses indicate a common reason rather than a direct causality for both phenomena. The time delay and low value of CT density changes provide a reasonable explanation for the higher sensitivity of MR imaging in ischemic stroke.
Insights
Diffusion-weighted MRI detects restricted water diffusion, while CT measures water uptake in acute ischemic stroke. Both show correlation, but MRI is more sensitive due to faster changes.
Area of Science:
- Neurology
- Radiology
- Medical Imaging
Background:
- Acute ischemic stroke involves restricted molecular water diffusion (detectable by DWI MRI) and net water uptake (detectable by CT).
- Understanding the relationship between these imaging findings is crucial for early diagnosis and management.
Purpose of the Study:
- To compare the decrease in apparent diffusion coefficient (ADC) on diffusion-weighted MR imaging with CT density changes.
- To investigate the correlation between diffusion restriction and water uptake in acute stroke patients.
Main Methods:
- Twenty-five acute ischemic stroke patients underwent MR and CT imaging within hours of symptom onset.
- ADC and CT data were spatially registered, and regions of decreased ADC were overlaid on CT scans.
- Mean ADC and CT density values were compared between affected and unaffected hemispheres.
Main Results:
- A mean decrease in ADC (dADC) of 170+/-53x10(-6) mm2/s correlated with a decrease in CT density (dCT) of 1.3+/-0.7 HU.
- CT density showed a linear decrease (0.4 HU/h), while ADC decrease was rapid, nearing completion by 1.5 hours.
- A significant correlation (r=0.41, P=0.04) was found between ADC decrease and CT density decrease.
Conclusions:
- The severity of diffusion restriction correlates with net water uptake in acute ischemic stroke.
- Different time courses suggest a common underlying cause rather than direct causality.
- The rapid changes in ADC and slower, less pronounced CT density changes explain MRI's higher sensitivity in early ischemic stroke detection.