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.