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Differences between gray matter and white matter water diffusion in stroke: diffusion-tensor MR imaging in 12
P Mukherjee1, M M Bahn, R C McKinstry
1Mallinckrodt Institute of Radiology, Washington University School of Medicine, St Louis, MO 63110, USA. MukherjeeP@mir.wustl.edu
Purpose:
To investigate differences in water diffusion between white matter and gray matter in acute to early subacute stroke with diffusion-tensor magnetic resonance (MR) imaging.
Materials And Methods:
Twelve patients with unilateral middle cerebral arterial infarcts were examined with diffusion tensor-encoded echo-planar MR imaging 17 hours to 5 days after stroke onset. Isotropic diffusion coefficient (D) and diffusion anisotropy (A(sigma)) images were computed. (D) values were measured in ischemic and contralateral gray matter and white matter by using A(sigma) images to differentiate white matter from gray matter. (D) images were compared with unidirectional and directionally averaged diffusion-weighted images.
Results:
In all patients, (D) images showed two distinct levels of diffusion reduction in the infarct; more severe reduction occurred exclusively in white matter. (D) values were significantly less in infarcted white matter than in infarcted gray matter, whereas (D) values in the contralateral white matter and gray matter were not significantly different. Relative to the contralateral side, (D) values in the infarct were reduced by 46% in white matter and by 31% in gray matter (P <.001). Diffusion-weighted imaging caused underestimation of the magnitude and, in some cases, the spatial extent of the white matter diffusion abnormality.
Conclusion:
Isotropic diffusion is more reduced in white matter than in gray matter in acute to early subacute middle cerebral arterial stroke. Diffusion-tensor imaging may be more sensitive than diffusion-weighted imaging to white matter ischemia.
Insights
In acute stroke, white matter shows greater diffusion reduction than gray matter. Diffusion-tensor imaging is more sensitive than diffusion-weighted imaging for detecting white matter ischemia.
Area of Science:
- Neuroimaging
- Stroke research
- Diffusion MRI
Background:
- Stroke significantly impacts brain tissue, affecting both white matter (WM) and gray matter (GM).
- Understanding differential tissue response to ischemia is crucial for early diagnosis and treatment.
- Diffusion-tensor imaging (DTI) offers advanced insights into tissue microstructure compared to conventional diffusion-weighted imaging (DWI).
Purpose of the Study:
- To compare water diffusion changes in WM and GM in acute to early subacute stroke patients.
- To evaluate the sensitivity of DTI in detecting ischemia in different brain tissue types.
Main Methods:
- Diffusion-tensor echo-planar MR imaging was performed on 12 patients with middle cerebral artery infarcts.
- Isotropic diffusion coefficient (D) and diffusion anisotropy (Aσ) were computed to quantify diffusion.
- D values were measured in ischemic and contralateral WM and GM, differentiating tissue types using Aσ.
Main Results:
- Infarcted WM exhibited significantly greater diffusion reduction (46%) than infarcted GM (31%).
- DTI revealed two distinct levels of diffusion reduction within the infarct, predominantly in WM.
- DWI underestimated the extent and magnitude of WM diffusion abnormalities compared to DTI.
Conclusions:
- White matter is more severely affected by isotropic diffusion reduction than gray matter in acute stroke.
- Diffusion-tensor imaging demonstrates superior sensitivity for detecting white matter ischemia compared to diffusion-weighted imaging.