Estimation of the macromolecular proton fraction and bound pool T2 in multiple sclerosis

This study used a model for magnetization transfer (MT) to estimate two underlying parameters: the macromolecular proton fraction (f) and the bound pool T-2 (T-2b) in patients with multiple sclerosis (MS). Sixty patients with clinically definite MS and 27 healthy controls were imaged using: (1) a dual echo fast spin echo sequence, (2) a MT sequence (with ten MT power and offset frequency combinations) and (3) proton density and T-1 weighted sequences (for T-1 relaxation time estimation). Fourteen normal- appearing white matter (NAWM) regions of interest (ROI) and six normal- appearing gray matter (NAGM) ROIs were outlined in all subjects. Lesions were also contoured in subjects affected by MS. The model was fitted to the data leading to estimates of T-2b and f. Results showed that T-2b was increased in lesions whereas f was reduced. In NAWM, f was decreased while T-2b was only increased in secondary progressive MS. NAWM f correlated modestly with disability. Further studies are needed to investigate the pathological basis of the abnormalities observed.