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Magnetisation transfer ratios of contrast-enhancing and nonenhancing lesions in multiple sclerosis
1Department of Neuroradiology, Scientific Institute HS Raffaele, University of Milan, Italy.
Abstract:
Magnetisation transfer (MT) is a recently introduced technique for assessing the water content of tissues in vivo and its relationship to macromolecules or membranes. It has been suggested that MT could provide indirect evidence of the characteristics of multiple sclerosis (MS) lesions (oedema, demyelination, or gliosis). Our aims were to characterise brain MS lesions and to compare the magnetisation transfer ratio (MTR) values of lesions with different patterns of contrast enhancement. In patients with MS we measured the MTR of 65 gadolinium-enhancing and 292 nonenhancing lesions. Using the equation published by Dousset et al. we studied 29 patients with clinically definite MS and 10 healthy controls. Lesions had significantly lower MT than the normal-appearing white matter of the patients or the normal white matter of healthy controls. There was no difference in the MTR of enhancing and nonenhancing lesions. Enhancement was homogeneous in 45 and ring-like in 20 lesions; MTR values were lower in the latter. These findings are presumably related to the differences in pathological features of enhancing (different amounts of proteins and inflammatory cells, oedema and demyelination) and nonenhancing (gliosis, demyelination and axonal loss) lesions.
Insights
Magnetisation transfer (MT) imaging reveals lower MTR values in multiple sclerosis (MS) lesions compared to normal white matter. MT imaging did not differentiate between enhancing and nonenhancing MS lesions, but ring-enhancing lesions showed lower MTR.
Area of Science:
- Neuroimaging
- Biophysics
Background:
- Magnetisation transfer (MT) is a novel in vivo technique for assessing tissue water content and its relation to macromolecules.
- MT imaging may offer insights into the pathological characteristics of multiple sclerosis (MS) lesions, including edema, demyelination, and gliosis.
Purpose of the Study:
- To characterize brain MS lesions using MT imaging.
- To compare Magnetisation Transfer Ratio (MTR) values in MS lesions with varying contrast enhancement patterns.
Main Methods:
- Magnetisation transfer ratio (MTR) was measured in 65 gadolinium-enhancing and 292 nonenhancing lesions in 29 patients with clinically definite MS.
- MTR values were compared between lesions and normal-appearing white matter (NAWM) in patients and healthy controls.
- Lesion enhancement patterns (homogeneous vs. ring-like) were analyzed in relation to MTR.
Main Results:
- MS lesions exhibited significantly lower MTR values compared to both patient NAWM and healthy control white matter.
- No significant difference in MTR was observed between gadolinium-enhancing and nonenhancing MS lesions.
- Ring-like enhancing lesions demonstrated lower MTR values than homogeneously enhancing lesions.
Conclusions:
- MT imaging can detect alterations in MS lesions, reflecting underlying tissue pathology.
- MTR values do not reliably distinguish between enhancing and nonenhancing MS lesions.
- Heterogeneity in MTR within enhancing lesions, particularly ring-like patterns, may correlate with specific pathological features such as edema, demyelination, and gliosis.