Choice of spectroscopic lineshape model affects metabolite peak areas and area ratios

The use of Lorentzian model lineshapes leads to systematic errors in the qu antification of in vivo H-1 NMR spectra, Experimental lineshapes are better modeled by the Voigt (mixed Lorentzian-Gaussian) function, leading to more accurate fits (reduced chi(2)). In this work, results from a group of 41 s ubjects are presented. It is shown that not only are the estimated metaboli te peak areas affected by the choice of lineshape model, but so too are the metabolite ratios. For example, the NAA/choline ratio was 1.92 +/- 0.06 (m ean +/- standard error) using the Lorentzian lineshape model and 1.85 +/- 0 .05 using the Voigt lineshape model. The corresponding figures for NAA/crea tine were 2.32 +/- 0.06 and 2.10 +/- 0.05 respectively, which are significa ntly different for the two lineshape models, An explanation of this previou sly unreported effect is given, This finding clearly has serious implicatio ns for the methodology and reporting of spectroscopic studies. (C) 2000 Wil ey-Liss, Inc.