Multiple sclerosis: Magnetization transfer histogram analysis of segmentednormal-appearing white matter

PURPOSE: To investigate and characterize the global distribution of magneti zation, transfer (MT) ratio values of normal-appearing white matter (NAWM) in patients with relapsing-remitting multiple sclerosis (MS) and test the h ypothesis that the MT histogram for NAWM reflects disease progression. MATE RIALS AND METHODS: Conventional and MT magnetic resonance (MR) Images were obtained in 23 patients and 25 healthy volunteers. Clinical tests for compa rison with the MT histogram parameters included the Extended Disability Sta tus Scale and the ambulation index. Lesion load calculated with T2-weighted MR images and whole-brain and white matter volumes were measured. RESULTS: The location of the MT histogram peak and the mean MT ratio for NAWM were significantly lower in patients with MS than in control subjects. In longit udinal studies, the histogram peak location and mean MT ratio shifted in th e direction of normal values as the duration of disease increased. A mean o f 26.5% of the volume of new lesions identified on the later studies were d emonstrated to have originated in NAWM corresponding to "lost" pixels on th e histogram. CONCLUSION: MT histogram analysis of NAWM, including longitudi nal analysis, may provide new prognostic information regarding lesion forma tion and increase understanding of the course of the disease.