Magnetization transfer and multicomponent T2 relaxation measurements with histopathologic correlation in an experimental model of MS

Magnetization transfer and multicomponent T2 imaging techniques were implem ented to study guinea pig in vivo. A chronic-progressive model of experimen tal allergic encephalomyelitis (EAE) was produced, and the inflammatory com ponent of the disease was manipulated using antibodies against integrin. Th e magnetization transfer ratio (MTR) and T2 relaxation properties were meas ured in normal-appearing white matter (NAWM) with histological comparisons. Significant reductions in both the mean MTR and the myelin water percentag e were measured in NAWM of EAE guinea pig brain. However, the MTR and myeli n water percentage appear to measure different aspects of pathology in NAWM in EAE. Reductions in the MTR were prevented or reversed with suppression of inflammation. However, modulation of inflammatory activity was not refle cted in the measurement of the myelin water percentage. Since the amount of myelin Is not expected to vary with inflammatory-related changes, these ob servations support our hypothesis that the MTR is sensitive to physiologica l changes to myelin induced by inflammation, while the short T2 component i s a more specific indicator of myelin content in tissue. Pathologic feature s other than demyelination may be important in the determination of the MTR . J. Magn. Reson. Imaging 2000;11:586-595. (C) 2000 Wiley-Liss, Inc.