MAGNETIZATION-TRANSFER RATIOS OF CONTRAST-ENHANCING AND NONENHANCING LESIONS IN MULTIPLE-SCLEROSIS

Magnetisation transfer (MT) is a recently introduced technique for ass essing the water content of tissues in vivo and its relationship to ma cromolecules or membranes. It has been suggested that MT could provide indirect evidence of the characteristics of multiple sclerosis (MS) l esions (oedema, demyelination, or gliosis). Our aims were to character ise 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 a nd 292 nonenhancing lesions. Using the equation published by Dousset e t al. we studied 29 patients with clinically definite MS and 10 health y controls. Lesions had significantly lower MT than the normal-appeari ng white matter of the patients or the normal white matter of healthy controls. There was no difference in the MTR of enhancing and nonenhan cing lesions. Enhancement was homogeneous in 45 and ring-like in 20 le sions; MTR values were lower in the latter. These findings are presuma bly related to the differences in pathological features of enhancing ( different amounts of proteins and inflammatory cells, oedema and demye lination) and nonenhancing (gliosis, demyelination and axonal loss) le sions.