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Diffusion tensor imaging of lesions and normal-appearing white matter in multiple sclerosis
D J Werring1, C A Clark, G J Barker
1NMR Research Unit, Institute of Neurology, the National Hospital for Neurology and Neurosurgery, London, UK.
Objective:
To determine whether diffusion tensor imaging (DTI) can detect structural changes in normal-appearing white matter, and to distinguish between plaques of different pathologic severity, in patients with MS.
Background:
Conventional MRI detects lesions sensitively in MS but has limited pathologic specificity. The diffusion of water molecules in brain tissue, most fully expressed mathematically by a tensor quantity, reflects its intrinsic microstructure. It is now possible to estimate the diffusion tensor noninvasively in the human brain using MR DTI. This method is unique in providing precise and rotationally invariant measurements of the amount and directional bias (anisotropy) of diffusion in white matter tracts relating to tissue integrity and orientation.
Methods:
DTI was performed in six patients with MS and in six age-matched control subjects. Diffusion was characterized in normal-appearing white matter in both groups, and in lesions of different pathologic subtypes (inflammatory, noninflammatory, T1 hypointense, and T1 isointense).
Results:
DTI identified significantly altered water diffusion properties in the normal-appearing white matter of patients compared with control subjects (p < 0.001), and distinguished between lesion types. The highest diffusion was seen in destructive (T1 hypointense) lesions, whereas the greatest change in anisotropy was found in inflammatory (gadolinium-enhancing) lesions.
Conclusions:
DTI detects diffuse abnormalities in the normal-appearing white matter of MS patients, and the findings in lesions appear to relate to pathologic severity. Its use in serial studies and in larger clinical cohorts may increase our understanding of pathogenetic mechanisms of reversible and persistent disability.
Insights
Diffusion Tensor Imaging (DTI) reveals subtle white matter changes in Multiple Sclerosis (MS) patients, differentiating lesion severity. This advanced MRI technique offers new insights into MS pathology.
Area of Science:
- Neuroimaging
- Biomedical Engineering
- Neurology
Background:
- Conventional MRI in Multiple Sclerosis (MS) shows lesions but lacks pathological specificity.
- Diffusion Tensor Imaging (DTI) quantifies water diffusion, reflecting white matter microstructure and integrity.
- DTI provides precise measurements of diffusion amount and anisotropy in white matter tracts.
Purpose of the Study:
- To assess DTI's capability in detecting structural changes in normal-appearing white matter in MS patients.
- To differentiate MS plaques based on their pathological severity using DTI.
- To investigate the relationship between DTI metrics and MS lesion characteristics.
Main Methods:
- DTI was performed on six MS patients and six age-matched controls.
- Diffusion properties were analyzed in normal-appearing white matter and various MS lesion subtypes.
- Lesions were categorized by inflammatory status and T1 signal intensity (hypointense, isointense).
Main Results:
- DTI demonstrated significantly altered water diffusion in the normal-appearing white matter of MS patients (p < 0.001).
- Distinct diffusion patterns were observed across different MS lesion types.
- Destructive (T1 hypointense) lesions showed the highest diffusion, while inflammatory (gadolinium-enhancing) lesions exhibited the greatest anisotropy change.
Conclusions:
- DTI effectively detects widespread abnormalities in the normal-appearing white matter of MS patients.
- DTI findings in MS lesions correlate with their pathological severity.
- Serial DTI studies in larger MS cohorts could enhance understanding of disability mechanisms.