Absolute molar concentrations by NMR in inhomogeneous B1. A scheme for analysis of in vivo metabolites

Keith R. Thulborn, Joseph J.H. Ackerman

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The use of multiple tuned radiofrequency coils is described as a method for obtaining absolute in vivo metabolite concentrations explicitly from high resolution chemical shift spectra and zeugmatographic spin images recorded using pulse Fourier transform NMR. Further delineation to intracellular concentrations by a complimentary NMR experiment is also discussed. In instances where the alternating magnetic field distribution, B1, is determined predominantly by coil geometry, the magnitude of B1 for a multiple tuned coil will map equally over space for each coil frequency and this allows the matching of flip angles over space for each nuclide of interest. In the particular case where one of the resonances under consideration is 1H from H2O, the ratio of signal intensities for two nuclides (e.g., 31P 1H) can be used to obtain the individual concentrations of each metabolite having a resonance (e.g., 31P) in the high resolution spectrum. More generally, the intensity ratio can be used to obtain a total concentration distribution for given nuclides in the spin image. This suggests a possible method for image contrast enhancement. The method is valid for uniform B1 as used in low frequency imaging (ca. ≤ 30 MHz) and with inhomogeneous B1 as produced by surface coils at higher frequencies. A brief background development is presented along with a discussion of the practical application and its demonstration using examples employing 1H, 23Na, 31P, and 39K NMR.

Original languageEnglish
Pages (from-to)357-371
Number of pages15
JournalJournal of Magnetic Resonance (1969)
Issue number3
StatePublished - Dec 1983

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