MAGNETIZATION-TRANSFER EFFECTS IN MR-DETECTED MULTIPLE-SCLEROSIS LESIONS - COMPARISON WITH GADOLINIUM-ENHANCED SPIN-ECHO IMAGES AND NONENHANCED T1-WEIGHTED IMAGES

PURPOSE: To define the relationship between magnetization transfer and blood-brain-barrier breakdown in multiple sclerosis lesions using gad olinium enhancement as an index of the latter. METHODS: Two hundred tw enty lesions (high-signal abnormalities on T2-weighted images) in 35 m ultiple sclerosis patients were studied with gadolinium-enhanced spin- echo imaging and magnetization transfer. Lesions were divided into gro ups having nodular or uniform enhancement, ring enhancement, or no enh ancement 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 appearan ce on the unenhanced T1-weighted images. RESULTS: There was no differe nce between the magnetization transfer ratio (MTR) of lesions as a fun ction of enhancement. MTR of hypointense lesions on unenhanced T1-weig hted images was, however, lower than the MTR of isointense lesions. CO NCLUSION: We speculate that diminished MTR may reflect diminished myel in 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 scle rosis lesions occurs centrifugally. In addition, the short-repetition- time pulse sequence seems useful in the evaluation of myelin loss in p atients with multiple sclerosis.