Abstract:
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Purpose: To use Diffusion Tensor Imaging (DTI) to determine the extent of abnormality in normal appearing white matter adjacent to demyelinating plaques, in comparison to values obtained in normal volunteers.
Methods and Materials: Ten MS plaques were studied in 7 subjects (4 female, mean age 34 years, range 25-54 years). Oval regions of interest (ROI) were placed by a single observer on plaque and anisotropy values recorded. An identical ROI was placed in the corresponding location in 5 normal controls. Six oval ROIs with a short-axis diameter half that of the original ROI were placed around the perimeter of each plaque and the corresponding areas in normal controls. Anisotropy values in plaques and adjacent white matter were compared to the averaged values for each ROI in normal controls. The DTI-determined extent of WM abnormality was evaluated for different thresholds (85%, 75% and 65% of value in normal subjects).
Results: Mean plaque size was 75mm2 (range 53-118mm2). Mean plaque anisotropy was 0.295 (range 0.219-0.505),compared to a mean value of 0.464 in controls (range 0.376-0.623), p<0.0001. The anisotropy of plaques was 62.5% (range 48-84%) that of the averaged corresponding normal WM in control cases. The mean anisotropy value in peri-plaque white matter (averaged over 6 ROIs) was 85% that seen in the control group (0.381 compared to 0.446), p=0.0027. In individual cases, the mean peri-plaque WM anisotropy was between 69 and 104% of the value in control subjects. Applying a threshold of anisotropy 85% that of normal, average plaque size increased from 75mm2 to 168mm2, or to 224% of the plaque size evident on T2 weighted images, p=0.0016. With a threshold of 75% of normal, average plaque size increased to 124 mm2 (165% of original plaque size, p=0.0087). Only one plaque showed no increase in size using these thresholds. There was no statistically significant change in plaque size when a 65% threshold was applied (p=0.08)
Conclusion: DTI shows a statistically significant reduction in anisotropy values in normal appearing WM adjacent to MS plaques compared to normal controls. DTI may represent a more accurate method of determining extent of demyelination than standard techniques.
Kealey MD, S,
Diffusion Tensor Imaging Assessment of Demyelinating Plaques and the Adjacent Normal Appearing White Matter in Multiple Sclerosis: A Comparison Study with Normal Controls. Radiological Society of North America 2003 Scientific Assembly and Annual Meeting, November 30 - December 5, 2003 ,Chicago IL.
http://archive.rsna.org/2003/3102765.html
