Abstract
BACKGROUND AND PURPOSE: Although NAA is often used as a marker of neural integrity and health in different neurologic disorders, the temporal behavior of WBNAA is not well characterized. Our goal therefore was to establish its normal variations in a cohort of healthy adults over typical clinical trial periods.
MATERIALS AND METHODS: Baseline amount of brain NAA, QNAA, was obtained with nonlocalizing proton MR spectroscopy from 9 subjects (7 women, 2 men; 31.2 ± 5.6 years old). QNAA was converted into absolute millimole amount by using phantom-replacement. The WBNAA concentration was derived by dividing QNAA with the brain parenchyma volume, VB, segmented from MR imaging. Temporal variations were determined with 4 annual scans of each participant.
RESULTS: The distribution of WBNAA levels was not different among time points with respect to the mean, 12.1 ± 1.5 mmol/L (P > .6), nor was its intrasubject change (coefficient of variation = 8.6%) significant between any 2 scans (P > .5). There was a small (0.2 mL) but significant (P = .05) annual VB decline.
CONCLUSIONS: WBNAA is stable over a 3-year period in healthy adults. It qualifies therefore as a biomarker for global neuronal loss and dysfunction in diffuse neurologic disorders that may be well worth considering as a secondary outcome measure candidate for clinical trials.
Footnotes
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- CV
- coefficient of variation
- GM
- gray matter
- 1H-MRS
- proton MR spectroscopy
- MPRAGE
- magnetization-prepared rapid acquisition of gradient echo
- NAA
- N-acetylaspartate
- QNAA
- absolute amount of NAA (millimoles)
- SNR
- signal intensity–to-noise ratio
- SR
- reference NAA peak area
- SS
- subject NAA peak area
- VOI
- volume of interest
- VR180°
- reference transmitter voltage
- VS180°
- subject transmitter voltage
- WBNAA
- whole-brain NAA concentration
- WM
- white matter
- © 2011 American Society of Neuroradiology
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