Edinburgh Napier University

  Quantification of NMR visible metabolites by spectral modeling
usually assumes a Lorentzian or Gaussian lineshape, despite
the fact that experimental lineshapes are neither. To
minimize systematic fitting errors, a mixed Lorentzian-Gaussian
(Voigt) lineshape model was developed. When tested with
synthetic FIDs, the Voigt lineshape model gave more accurate
results (maximum error 2%) than either Lorentzian (maximum
error 20%) or Gaussian models (maximum error 12%). The
three lineshape models gave substantially different peak areas
in an in vitro experiment, with the Voigt model having a
much lower 3 (2.1 compared with 5.2 for the Lorentzian
model and 6.2 for the Gaussian model). In a group of 10
healthy volunteers, fitting of ’H spectra from cerebral white
matter gave significantly different peak areas between the
methods. Even when area ratios were taken, the Lorentzian
model gave higher values (+5% for “Vcholine and +2% for
Nucreatine) than the Voigt lineshape model, whereas the
Gaussian model gave lower values (-2% and -1v0, respectively.