Proton MRS of large multiple sclerosis lesions reveals subtle changes in metabolite T 1 and area

The T 1 values of metabolites were measured in eight subjects with clinically definite multiple sclerosis (MS) having at least one large brain lesion (2.6 ± 0.7 mL) and in eight age‐ and sex‐matched healthy controls. MRS examinations were conducted at 1.5 T using point‐resolved spectroscopy (PRESS) (TE = 30 ms, TR = 530, 750, 1200, 1500, 3500, 5000 ms). Spectra were acquired from a voxel placed in the largest lesion in the subject with MS, and in a corresponding voxel (same size and region) in normal white matter (NWM) in the matched control, and were fitted using LCModel. As there are regional variations in metabolite and water T 1 and metabolite signal areas, careful placement of the control voxel was necessary to measure subtle differences between the lesions and NWM. The T 1 and T 1 ‐corrected signal areas of creatine were the same in MS lesions as in controls. The T 1 values of choline were significantly shorter in MS lesions located in occipital and parietal, but not in frontal, white matter. N ‐Acetylaspartate (NAA) and myoinositol T 1 values in MS lesions were similar to those in NWM; however, the area of myoinositol correlated directly with lesion water T 1 , and the area of NAA correlated inversely with lesion water T 1 . MR spectra acquired at short TR require T 1 correction of choline for accurate quantification. Careful voxel placement in controls to match lesion location in subjects with MS enables a clearer view of the subtle changes in lesions. Copyright © 2010 John Wiley & Sons, Ltd.