MR spectroscopy in the evaluation of enhancing lesions in the brain in multiple sclerosis.

PURPOSE To compare proton MR spectroscopic alterations with the degree of contrast enhancement in multiple sclerosis (MS) lesions. METHODS Thirty-five patients with clinically diagnosed MS were studied with MR spectroscopy. A total of 47 lesions were examined. Solvent-suppressed proton spectra were acquired with an echo time of 16 milliseconds using the point-resolved spectroscopic localization method from 1.5 cm3 voxels. Marker peaks/creatine (Cr) ratios obtained from these spectra were plotted against the relative enhancement of the lesion seen after administration of contrast material. The relative enhancement was defined as S(contrast) -S0/S0, where S0 is the signal intensity of a T1-weighted image and S(contrast) is the signal intensity after administration of gadopentetate dimeglumine. RESULTS We found a positive linear relationship between the marker peaks/Cr ratio and the degree of enhancement of the lesion. That is, the marker peaks/Cr ratio was higher in the lesions that showed the greatest enhancement. CONCLUSION The MR/Cr ratio obtained with the use of short-echo-time proton MR spectroscopy correlates with the degree of contrast enhancement. This ratio may therefore serve as a means for evaluating and quantifying the level of inflammatory activity within the plaques of patients with MS.