Reproducibility of proton magnetic resonance spectroscopy imaging measurements of normal human hippocampus at 1.5 T: Clinical implications

The authors investigate the reproducibility of metabolite signals measured with proton magnetic resonance spectroscopy (H-1-MRS) acquired from the hum an hippocampus in controls and in a phantom. Two H-1-MRS studies separated by 3 weeks were performed in 8 healthy volunteers and in a phantom. N-acety l compounds (NA), choline (Ch), and creatine (Cr) peak areas and ratios wer e measured and compared using percentage variation, and Pearson Correlation Coefficient at the level of every voxel, the level of 1 hippocampus (5 vox els), and the level of 2 hippocampi (10 voxels). Sensitivity for observing clinically significant between-session H-1-MRS changes was evaluated using the reliable change index. Reproducibility measures for metabolite peak are as were only moderately concordant with percentage variation ranging from 1 4% to 20% for NA, Cho, and Cr. Stability was much improved when NA ratios a nd sum of multiple voxels were considered. Between-session NA/(Cho + Cr) ch anges greater than 22%, 12%, and 10% in one given participant can be detect ed with a 90% confidence interval when considered at the single-voxel level , the level of a single hippocampus, or the level of both hippocampi, respe ctively. Left-right asymmetry indices showed similar and limited inter- hem ispheric asymmetry in repeated examination. This study suggests that 1H-MRS reproducibility performance is adequate for the study and monitoring of hu man hippocampus function when NA ratios and the sum of multiple voxels are considered. Individual metabolite peaks and single-voxel measurements have low reproducibility at 1.5 T and should be used only with clearly establish ed statistical parameters.