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Multiple sclerosis: diffusion tensor MR imaging for evaluation of normal-appearing white matter
Alexander C Guo1, James R MacFall, James M Provenzale
1Department of Radiology, Duke University Medical Center, Box 3808, Rm 1533, Erwin Rd, Durham, NC 27710-3808, USA.
Purpose:
To determine whether the normal-appearing white matter (NAWM) regions surrounding and remote from multiple sclerosis (MS) plaques have abnormal diffusional anisotropy and to compare anisotropy maps with apparent diffusion coefficient (ADC) maps for sensitivity in the detection of white matter (WM) abnormalities.
Materials And Methods:
Conventional and diffusion tensor magnetic resonance (MR) imaging examinations were performed in 26 patients with MS and in 26 age-matched control subjects. Fractional anisotropy (FA) and ADC maps were generated and coregistered with T2-weighted MR images. Uniform regions of interest were placed on plaques, periplaque white matter (PWM) regions, NAWM regions in the contralateral side of the brain, and WM regions in control subjects to obtain FA and ADC values, which were compared across the WM regions.
Results:
The mean FA was 0.280 for plaques, 0.383 for PWM, 0.493 for NAWM, and 0.537 for control subject WM. The mean ADC was 1.025 x 10(-3) mm(2)/sec for plaques, 0.786 x 10(-3) mm(2)/sec for PWM, 0.739 x 10(-3) mm(2)/sec for NAWM, and 0.726 x 10(-3) mm(2)/sec for control subject WM. Significant differences in anisotropy and ADC values were observed among all WM regions (P <.001 for all comparisons, except ADC in NAWM vs control subject WM [P =.018]).
Conclusion:
The anisotropy and ADC values were abnormal in all WM regions in the patients with MS and were worse in the periplaque regions than in the distant regions. Diffusion tensor MR imaging may be more accurate than T2-weighted MR imaging for assessment of disease burden.
Insights
Diffusion tensor imaging reveals white matter abnormalities in multiple sclerosis (MS) patients, even in normal-appearing white matter (NAWM) and periplaque regions. Fractional anisotropy (FA) and apparent diffusion coefficient (ADC) mapping can detect these subtle changes.
Area of Science:
- Neurology
- Radiology
- Biomedical Imaging
Background:
- Multiple sclerosis (MS) is a demyelinating disease affecting white matter (WM) in the brain.
- Subtle WM abnormalities may exist in regions appearing normal on conventional MRI.
- Diffusion tensor imaging (DTI) offers advanced characterization of WM microstructure.
Purpose of the Study:
- To investigate diffusional anisotropy in normal-appearing white matter (NAWM) surrounding and remote from MS plaques.
- To compare the sensitivity of fractional anisotropy (FA) and apparent diffusion coefficient (ADC) maps for detecting WM abnormalities in MS.
Main Methods:
- Diffusion tensor magnetic resonance imaging (DTI) and conventional MRI were performed on 26 MS patients and 26 controls.
- FA and ADC maps were generated and coregistered with T2-weighted images.
- Regions of interest were placed on plaques, periplaque WM (PWM), NAWM, and control WM to compare FA and ADC values.
Main Results:
- Mean FA values were significantly lower in MS plaques (0.280), PWM (0.383), and NAWM (0.493) compared to controls (0.537).
- Mean ADC values were significantly higher in MS plaques (1.025 x 10(-3) mm(2)/sec) and PWM (0.786 x 10(-3) mm(2)/sec) compared to controls (0.726 x 10(-3) mm(2)/sec).
- Significant differences in FA and ADC were observed across all WM regions in MS patients compared to controls.
Conclusions:
- WM regions in MS patients, including NAWM and periplaque areas, exhibit abnormal FA and ADC values.
- Diffusion tensor imaging, particularly FA and ADC mapping, is more sensitive than T2-weighted imaging for assessing MS disease burden.
- DTI can detect microstructural white matter damage in MS beyond what is visible on conventional MRI.