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P3‐182: 7T magnetic resonance spectroscopy of the hippocampus in mild cognitive impairment
Author(s) -
Penner Jacob,
Smith Matthew,
Wells Jennie,
Campbell Marybelle,
Borrie Michael,
Bartha Robert
Publication year - 2012
Publication title -
alzheimer's and dementia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.713
H-Index - 118
eISSN - 1552-5279
pISSN - 1552-5260
DOI - 10.1016/j.jalz.2012.05.1402
Subject(s) - metabolite , creatine , nuclear magnetic resonance , hippocampus , magnetic resonance imaging , choline , voxel , nuclear medicine , chemistry , medicine , physics , radiology
Background: Mild cognitive impairment (MCI) is a state of cognitive decline that is often found before the criteria for Alzheimer disease (AD) are met. ProtonMagnetic Resonance Spectroscopy (1 HMRS) has been previously used to monitor metabolite level changes in brain tissue in subjects with MCI. The use of high fields increases signal to noise ratio and spectral dispersion leading to improved metabolite quantification. The purpose of this study was to quantify metabolic changes in the hippocampus over time in subjects with mild cognitive impairment. Methods: A 7T Agilent/ Siemens head-only MRI system was used to acquire images and singlevoxel short-echo-time 1 H MR from the hippocampus of five subjects with MCI (3 males, age 686 11 years) at baseline. Cognition was measured with the MMSE and the MoCA. T 2 -weighted images (1x1x1.5 mm 3 resolution, TR 1⁄4 1s, TE 1⁄4 5.3 ms) were acquired for MRS voxel placement. Single-voxel 1 H MRS data were acquired from an average 2.7 6 0.7 cm 3 volume of interest (localization by adiabatic selective refocusing, TR 1⁄4 3.7s, TE 1⁄4 38 ms) in the hippocampus. The metabolite spectra were fit to determine the contribution of each metabolite to the spectrum. N -acetylaspartate (NAA), choline (Cho), myo-inositol (Myo), and glutamate (Glu) were measured and normalized to creatine (Cr) (which typically remains constant even in neuropathological conditions) for evaluation of changes over time. Results: The average baseline ratios were NAA/Cr 1⁄4 2.07 6 0.68, Glu/Cr 1⁄4 1.25 6 0.25, Myo/Cr 1⁄4 1.60 6 0.64, and Cho/Cr 1⁄4 1.30 6 0.55. Furthermore, the average signal/noise ratio (SNR) per volume for this study was 3.56 1.5. The average MMSE and MoCA scores at baseline were 26.8 6 1.8 and 25.4 6 0.9, respectively. Conclusions: In a previous study at 4T the average SNR/volume was 2.0 6 0.7. The 75% increase in SNR/volume reported in the current study is in agreement with the theoretically expected linear increase in SNR as a function of field strength. Follow-up scans will be performed to measure the change in metabolite ratios over time and to correlate with cognitive scores. Additional subjects will be recruited to provide greater statistical power.