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Magnetization transfer effects in MR-detected multiple sclerosis lesions: comparison with gadolinium-enhanced
J F Hiehle1, R I Grossman, K N Ramer
1Department of Radiology, Hospital of the University of Pennsylvania, Philadelphia 19104-4283.
Purpose:
To define the relationship between magnetization transfer and blood-brain-barrier breakdown in multiple sclerosis lesions using gadolinium enhancement as an index of the latter.
Methods:
Two hundred twenty lesions (high-signal abnormalities on T2-weighted images) in 35 multiple sclerosis patients were studied with gadolinium-enhanced spin-echo imaging and magnetization transfer. Lesions were divided into groups having nodular or uniform enhancement, ring enhancement, or no enhancement after gadolinium administration. For 133 lesions, T1-weighted images without contrast enhancement were also analyzed. These lesions were categorized as isointense or hypointense based on their appearance on the unenhanced T1-weighted images.
Results:
There was no difference between the magnetization transfer ratio (MTR) of lesions as a function of enhancement. MTR of hypointense lesions on unenhanced T1-weighted images was, however, lower than the MTR of isointense lesions.
Conclusion:
We speculate that diminished MTR may reflect diminished myelin content and that hypointensity on T1-weighted images corresponds to demyelination. Central regions of ring-enhancing lesions had a lower MTR than the periphery, suggesting that demyelination in multiple sclerosis lesions occurs centrifugally. In addition, the short-repetition-time pulse sequence seems useful in the evaluation of myelin loss in patients with multiple sclerosis.