title: Maximum entropy estimation of glutamate and glutamine in MR spectroscopic imaging.
abstract: Magnetic resonance spectroscopic imaging (MRSI) is often used to estimate the concentration of several brain metabolites. Abnormalities in these concentrations can indicate specific pathology, which can be quite useful in understanding the disease mechanism underlying those changes. Due to higher concentration, metabolites such as N-acetylaspartate (NAA), Creatine (Cr) and Choline (Cho) can be readily estimated using standard Fourier transform techniques. However, metabolites such as Glutamate (Glu) and Glutamine (Gln) occur in significantly lower concentrations and their resonance peaks are very close to each other making it difficult to accurately estimate their concentrations (separately). In this work, we propose to use the theory of 'Spectral Zooming' or high-resolution spectral analysis to separate the Glutamate and Glutamine peaks and accurately estimate their concentrations. The method works by estimating a unique power spectral density, which corresponds to the maximum entropy solution of a zero-mean stationary Gaussian process. We demonstrate our estimation technique on several physical phantom data sets as well as on in-vivo brain spectroscopic imaging data. The proposed technique is quite general and can be used to estimate the concentration of any other metabolite of interest.
authors.forename: Yogesh
authors.initials: Y
authors.lastname: Rathi
authors.forename: Lipeng
authors.initials: L
authors.lastname: Ning
authors.forename: Oleg
authors.initials: O
authors.lastname: Michailovich
authors.forename: HuiJun
authors.initials: H
authors.lastname: Liao
authors.forename: Borjan
authors.initials: B
authors.lastname: Gagoski
authors.forename: P Ellen
authors.initials: PE
authors.lastname: Grant
authors.forename: Martha E
authors.initials: ME
authors.lastname: Shenton
authors.forename: Robert
authors.initials: R
authors.lastname: Stern
authors.forename: Carl-Fredrik
authors.initials: CF
authors.lastname: Westin
authors.forename: Alexander
authors.initials: A
authors.lastname: Lin
mesh_terms: D000465:Algorithms; D015415:Biomarkers / Q000378:metabolism; D001921:Brain / Q000033:anatomy & histology / Q000378:metabolism*; D019277:Entropy; D018698:Glutamic Acid / Q000378:metabolism*; D005973:Glutamine / Q000378:metabolism*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D057054:Molecular Imaging / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014018:Tissue Distribution
chemical_list: D015415:Biomarkers; D005973:Glutamine; D018698:Glutamic Acid