Proton MR spectroscopy in mild cognitive impairment and Alzheimer disease: Comparison of 1.5 and 3 T

BACKGROUND AND PURPOSE: Theoretically, proton (¹H) MR spectroscopy at a higher field strength has the advantages of higher signal-to-noise ratio and improved spectral resolution. We therefore compared the ability of single-voxel ¹H MR spectroscopy at 1.5 and 3 T to diagnostically discriminate among cognitively normal elderly subjects, patients with mild cognitive impairment (MCI), and patients with Alzheimer disease (AD). METHODS: At both 1.5 and 3 T, we studied 41 cognitively normal elderly subjects, 20 patients with MCI, and 20 patients with AD. In each subject, ¹H MR spectroscopy was performed at TEs of 30 and 135 ms and from voxels placed over the posterior cingulate gyri. RESULTS: Average line widths and interexamination variability of metabolite ratios were higher at 3 T than at 1.5 T. Consistent quantification of glutamine (Gln) + glutamate/creatine (Cr) and Gln/Cr peak ratios occurred at 3 T but not at 1.5 T. Choline (Cho)/Cr (at TE = 135 ms) and myo-inositol (MI)/Cr were higher and N-acetylaspartate (NAA)/Cr (at TE = 135 ms) and NAA/MI were lower in patients with MCI than in cognitively normal subjects only at 1.5 T. MI/Cr and Cho/Cr were higher and NAA/Cr and NAA/MI were lower in patients with AD than in cognitively normal subjects at both 1.5 and 3 T. Differentiation of patients with AD from cognitively normal subjects by using the NAA/MI data was similar at both field strengths (P > .05). CONCLUSION: With currently available technology, the diagnostic performance of ¹H MR spectroscopy in patients with MCI and those with AD was not better at 3 T than at 1.5 T.