Automatic quantitation of localized <i>in vivo</i>¹H spectra with LCModel

TLDR

LCModel analyzes an in vivo spectrum as a linear combination of complete model in vitro spectra from individual metabolite solutions, incorporating maximum prior information. The study illustrates the capabilities and limitations of LCModel and proton MRS across field strengths from 1.5 to 9.4 T and a wide range of sequences, particularly short TE. LCModel employs a nearly model‑free constrained regularization that automatically accounts for baseline and lineshape without imposing a restrictive parameterized form, analyzing spectra from diverse fields and sequences. LCModel automatically yields maximum‑likelihood estimates of metabolite concentrations and their uncertainties (Cramér‑Rao lower bounds) without subjective input. © 2001 John Wiley & Sons, Ltd.

Abstract

Abstract The LCModel method analyzes an in vivo spectrum as a Linear Combination of Model in vitro spectra from individual metabolite solutions. Complete model spectra, rather than individual resonances, are used in order to incorporate maximum prior information into the analysis. A nearly model‐free constrained regularization method automatically accounts for the baseline and lineshape in vivo without imposing a restrictive parameterized form on them. LCModel is automatic (non‐interactive) with no subjective input. Approximately maximum‐likelihood estimates of the metabolite concentrations and their uncertainties (Cramér‐Rao lower bounds) are obtained. LCModel analyses of spectra from users with fields from 1.5 to 9.4 T and a wide range of sequences, particularly with short TE , are used here to illustrate the capabilities and limitations of LCModel and proton MRS. Copyright © 2001 John Wiley &amp; Sons, Ltd. Abbreviations used: Ala alanine Asp aspartate Cr creatine GABA γ‐aminobutyric acid Glc glucose Gln glutamine Glu glutamate GPC glycerophosphocholine GSH glutathione Ins myo ‐inositol Lac lactate NAA N ‐acetylaspartate NAAG N ‐acetylaspartylglutamate PC phosphocholine PCr phosphocreatine PE phosphoethanolamine Scyllo scyllo ‐inositol S/N signal‐to‐noise ratio Tau taurine.