Abstract |
Total N-acetyl-aspartate + N-acetyl-aspartate- glutamate (NAA), total creatine (Cr) and total choline (Cho) proton MRS (1 H-MRS) signals are often used as surrogate markers in diffuse neurological pathologies, but spatial coverage of this methodology is limited to 1%-65% of the brain. Here we wish to demonstrate that non-localized, whole-head (WH) 1 H-MRS captures just the brain's contribution to the Cho and Cr signals, ignoring all other compartments. Towards this end, 27 young healthy adults (18 men, 9 women), 29.9 ± 8.5 years old, were recruited and underwent T1 -weighted MRI for tissue segmentation, non-localizing, approximately 3 min WH 1 H-MRS (TE /TR /TI = 5/10/940 ms) and 30 min 1 H-MR spectroscopic imaging (MRSI) (TE /TR = 35/2100 ms) in a 360 cm3 volume of interest (VOI) at the brain's center. The VOI absolute NAA, Cr and Cho concentrations, 7.7 ± 0.5, 5.5 ± 0.4 and 1.3 ± 0.2 mM, were all within 10% of the WH: 8.6 ± 1.1, 6.0 ± 1.0 and 1.3 ± 0.2 mM. The mean NAA/Cr and NAA/Cho ratios in the WH were only slightly higher than the "brain-only" VOI: 1.5 versus 1.4 (7%) and 6.6 versus 5.9 (11%); Cho/Cr were not different. The brain/WH volume ratio was 0.31 ± 0.03 (brain ≈ 30% of WH volume). Air-tissue susceptibility-driven local magnetic field changes going from the brain outwards showed sharp gradients of more than 100 Hz/cm (1 ppm/cm), explaining the skull's Cr and Cho signal losses through resonance shifts, line broadening and destructive interference. The similarity of non-localized WH and localized VOI NAA, Cr and Cho concentrations and their ratios suggests that their signals originate predominantly from the brain. Therefore, the fast, comprehensive WH-1 H-MRS method may facilitate quantification of these metabolites, which are common surrogate markers in neurological disorders.
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Authors | Ivan I Kirov, William E Wu, Brian J Soher, Matthew S Davitz, Jeffrey H Huang, James S Babb, Mariana Lazar, Girish Fatterpekar, Oded Gonen |
Journal | NMR in biomedicine
(NMR Biomed)
Vol. 30
Issue 10
(Oct 2017)
ISSN: 1099-1492 [Electronic] England |
PMID | 28678429
(Publication Type: Journal Article)
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Copyright | Copyright © 2017 John Wiley & Sons, Ltd. |
Chemical References |
- Protons
- Aspartic Acid
- N-acetylaspartate
- Creatine
- Choline
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Topics |
- Adolescent
- Adult
- Aspartic Acid
(analogs & derivatives)
- Brain
(metabolism)
- Choline
(metabolism)
- Creatine
(metabolism)
- Female
- Humans
- Magnetic Resonance Spectroscopy
(methods)
- Male
- Middle Aged
- Protons
- Young Adult
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