Magnetisation transfer imaging in multiple sclerosis.

Magnetisation transfer imaging (MTI) is a magnetic resonance imaging (MRI) technique that has a higher specificity than conventional T2-weighted scans to the heterogeneous pathological substrates of multiple sclerosis (MS) lesions. This review outlines the contribution of MTI in the study of lesion evolution and in the assessment of disease burden in MS. MTI studies of individual MS lesions confirm the pathological heterogeneity of T2-weighted MRI abnormalities and the potential role of unenhanced T1-weighted hypointensities as specific markers of localised severe white matter disruption. Correlative cross-sectional and longitudinal studies using MTI and gadolinium (Gd)-enhanced MRI reveal that MTI findings may vary in lesions with different patterns of enhancement, and that MTI abnormalities are closely related to the onset and recovery of blood-brain barrier disruption in new MS plaques. Measures obtained from MTI scans using whole-brain histogram analysis are highly correlated with the extent of MS abnormalities on conventional MRI scans and predict patients' clinical disability well, since they are sensitive to the amounts of both macro- and microscopic MS disease burden in the whole brain and in specific regions.