Proton nuclear magnetic resonance lineshape studies on human blood plasma lipids from newborn infants, healthy adults, and adults with tumors

MR spectroscopy quantitation: a review of frequency domain methods

There has been a vast increase in applications of magnetic resonance spectroscopy (MRS) in biomedical research during the last few years. This is not surprising since MRS provides both in vivo and in vitro a non-invasive tool for various biochemical and biomedical studies. There are also expectations that clinical MRS will have an important role as a diagnostic tool. An essential prerequisite for the future success of MRS for applicability in biomedical sciences will be accurate and biochemically relevant data analysis (at as high a level of automation as possible). This review briefly describes principles of the methodology available for advanced quantitative data analysis in the frequency domain. Various biomedical applications are discussed in order to illustrate the practical aspects of the analyses and to show the applicability and power of biochemical prior knowledge-based lineshape fitting analysis.

Quantification of plasma lipoprotein fractions by wavelet transform time-domain data processing of the proton nuclear magnetic resonance methylene spectral region

Quantitative analysis of lipoprotein major fractions, LDL, VLDL and HDL, is of great interest for medical purposes, for instance in liver or heart diseases, diet management or cancer. The presently available biochemical methods require time consuming ultracentrifugation. A potentially automated method is proposed, using time domain quantification by Wavelet Transform (WT-NMR) method. The aim of the present study was to evaluate, on a preliminary series of nine human plasmas, the potential interest of WT-NMR in the quantification of both NMR-visible lipids and total lipoprotein fractions. The correlation coefficients between low and intermediate density (LDL+IDL), very low density (VLDL) and high density (HDL) lipoprotein visible lipid quantifications, obtained on nine human plasmas with WT-NMR and standard biochemical methods, were 0.79, 0.84 and 0.92, respectively. For the total lipoprotein assay, i.e. including an estimation of non NMR-visible protein and free cholesterol, the correlation between WT-NMR and the biochemistry were 0.87 for LDL+IDL, 0.81 for VLDL and 0.88 for HDL.

Time and frequency domain analysis of NMR data compared: an application to 1D 1H spectra of lipoproteins

A comparison between a time domain analysis algorithm (VARPRO) and a frequency domain analysis algorithm (FITPLAC) for parameter estimation of magnetic resonance spectroscopy (MRS) data series is presented. VARPRO analyses the measured MRS signal (free induction decay; FID); FITPLAC analyses the discrete Fourier transform of the FID, the frequency domain magnetic resonance spectrum. A rapid time domain method, used to subtract the dominating water resonance from a 1H MRS FID, without affecting the metabolites of interest, is outlined and applied. Also a new "pseudofrequency selective" approach to time domain fitting is introduced. The possibilities of combining the most favorable features of time and frequency domain processing into one single MRS signal processing method are assessed. The 1H MRS signals of ultracentrifuged very low (VLDL), intermediate (IDL), and high (HDL) density lipoprotein fractions from human blood plasma were used for the comparisons. The results from both algorithms were in good agreement.

A comparative study of 1H NMR lineshape fitting analyses and biochemical lipid analyses of the lipoprotein fractions VLDL, LDL and HDL, and total human blood plasma

The purpose of this work was two-fold. In the first instance, 1H NMR spectra of the ultracentrifuged lipoprotein fractions (VLDL, LDL and HDL) from six volunteers with different clinical conditions were measured. The methylene regions of the experimental spectra were modelled in the frequency domain using non-linear lineshape fitting analyses. In this way the resolvable Lorentzian component structures of the methylene regions of these lipoprotein fraction spectra could be determined. Second, the lipoprotein fraction analyses were used to construct simplified component structures, which interpreted the lipoprotein fraction spectra well, and were feasible to use in the total plasma spectra analyses. The considerable overlap problem of the resonances was properly handled in this way. The NMR-based relative amounts of the lipoproteins (relative integrated intensities of the lipoprotein model signals) obtained were compared to the biochemically resolved relative molar percentages of the lipoprotein fractions and also of the lipid contents between the lipoprotein complexes. It was noticed that nearly all correlations were extremely good. Thus, it is suggested that the developed methodology could be used as a fast method to predict the relative amounts of the lipoproteins and also possibly the relative lipid contents between the major lipoprotein categories directly from the proton NMR spectrum of a total blood plasma sample. Furthermore, if internal or external reference for the integrated intensities of the proton NMR resonances were used, it should also be possible to obtain the absolute amounts of these quantities.