title: Automated whole-brain N-acetylaspartate proton MRS quantification.
abstract: Concentration of the neuronal marker, N-acetylaspartate (NAA), a quantitative metric for the health and density of neurons, is currently obtained by integration of the manually defined peak in whole-head proton ((1) H)-MRS. Our goal was to develop a full spectral modeling approach for the automatic estimation of the whole-brain NAA concentration (WBNAA) and to compare the performance of this approach with a manual frequency-range peak integration approach previously employed. MRI and whole-head (1) H-MRS from 18 healthy young adults were examined. Non-localized, whole-head (1) H-MRS obtained at 3 T yielded the NAA peak area through both manually defined frequency-range integration and the new, full spectral simulation. The NAA peak area was converted into an absolute amount with phantom replacement and normalized for brain volume (segmented from T1 -weighted MRI) to yield WBNAA. A paired-sample t test was used to compare the means of the WBNAA paradigms and a likelihood ratio test used to compare their coefficients of variation. While the between-subject WBNAA means were nearly identical (12.8 ± 2.5 mm for integration, 12.8 ± 1.4 mm for spectral modeling), the latter's standard deviation was significantly smaller (by ~50%, p = 0.026). The within-subject variability was 11.7% (±1.3 mm) for integration versus 7.0% (±0.8 mm) for spectral modeling, i.e., a 40% improvement. The (quantifiable) quality of the modeling approach was high, as reflected by Cramer-Rao lower bounds below 0.1% and vanishingly small (experimental - fitted) residuals. Modeling of the whole-head (1) H-MRS increases WBNAA quantification reliability by reducing its variability, its susceptibility to operator bias and baseline roll, and by providing quality-control feedback. Together, these enhance the usefulness of the technique for monitoring the diffuse progression and treatment response of neurological disorders.
authors.affiliation: Department of Radiology, Duke University Medical Center, Durham, NC, 27710, USA.
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Soher
authors.forename: William E
authors.initials: WE
authors.lastname: Wu
authors.forename: Assaf
authors.initials: A
authors.lastname: Tal
authors.forename: Pippa
authors.initials: P
authors.lastname: Storey
authors.forename: Ke
authors.initials: K
authors.lastname: Zhang
authors.forename: James S
authors.initials: JS
authors.lastname: Babb
authors.forename: Ivan I
authors.initials: II
authors.lastname: Kirov
authors.forename: Yvonne W
authors.initials: YW
authors.lastname: Lui
authors.forename: Oded
authors.initials: O
authors.lastname: Gonen
mesh_terms: D000328:Adult; D001224:Aspartic Acid / Q000031:analogs & derivatives* / Q000032:analysis; D001331:Automation; D001921:Brain / Q000033:anatomy & histology; D001923:Brain Chemistry; D003198:Computer Simulation; D005260:Female; D006801:Humans; D008297:Male; D009474:Neurons / Q000378:metabolism; D009929:Organ Size; D019047:Phantoms, Imaging; D066244:Proton Magnetic Resonance Spectroscopy / Q000295:instrumentation / Q000379:methods*; D011522:Protons; D012016:Reference Values
chemical_list: D011522:Protons; D001224:Aspartic Acid; C000179:N-acetylaspartate
keywords: MRI segmentation; MRS quantification; N-acetylaspartate (NAA); whole-brain NAA concentration (WBNAA)