Combined magnetization transfer and proton spectroscopic imaging in the assessment of pathologic brain lesions in multiple sclerosis

BACKGROUND AND PURPOSE: Conventional MR imaging of multiple sclerosis (MS) provides relatively poor pathologic specificity, which has led to the inves tigation of more sophisticated MR techniques, The purpose of this study was to combine magnetization transfer (MT) imaging and proton MR spectroscopic imaging (MRSI) to evaluate the specific pathologic features of myelination and neuronal integrity in patients with MS and to determine the relationsh ip between these measures within plaques. METHODS: We acquired conventional MR, MT, and proton MRSI data and evaluate d clinical disability in 30 patients with MS, whose conditions were categor ized as relapsing-remitting, primary progressive, or secondary progressive, The lesions were classified, using a semiautomated edge-following techniqu e, on T2-weighted MR images, and an analysis of MT and proton MRSI data was conducted for lesion regions as well as for tissue that was categorized as normal. RESULTS: The MT ratio (MTR) of normal-appearing white matter in the patient s,vith MS was significantly lower than in the healthy participants, whereas gray matter values were unchanged, MS lesions showed a large reduction in MTR, with old lesions exhibiting a lower MTR than new lesions, The average lesion MTR and the MR spectroscopic imaging-measured relative concentration of N-acetylaspartate, a marker of neuronal integrity, was positively corre lated in patients with relapsing-remitting MS, This relationship was streng thened in regions containing new lesions. CONCLUSION: The integrated use of MT and MR spectroscopic imaging provides a more complete description of the pathologic features of MS than does conv entional MR imaging alone, and our data suggest that axonal damage occurs i n step with new demyelination and is not a late feature of the disease.