Temperature dependence of 1H NMR chemical shifts and its influence on estimated metabolite concentrations
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Temperature dependent chemical shifts of important brain metabolites measured by localised 1H MRS were investigated to test how the use of incorrect prior knowledge on chemical shifts impairs the quantification of metabolite concentrations.
Materials and methods
Phantom measurements on solutions containing 11 metabolites were performed on a 7 T scanner between 1 and 43 °C. The temperature dependence of the chemical shift differences was fitted by a linear model. Spectra were simulated for different temperatures and analysed by the AQSES program (jMRUI 5.2) using model functions with chemical shift values for 37 °C.
Large differences in the temperature dependence of the chemical shift differences were determined with a maximum slope of about ±7.5 × 10−4 ppm/K. For 32–40 °C, only minor quantification errors resulted from using incorrect chemical shifts, with the exception of Cr and PCr. For 1–10 °C considerable quantification errors occurred if the temperature dependence of the chemical shifts was neglected.
If 1H MRS measurements are not performed at 37 °C, for which the published chemical shift values have been determined, the temperature dependence of chemical shifts should be considered to avoid systematic quantification errors, particularly for measurements on animal models at lower temperatures.
KeywordsNMR spectroscopy Spectrum analysis Brain metabolites Polar organisms
Automated quantitation of short echo time MRS spectra
Chemical exchange saturation transfer
Fast automatic shimming technique by mapping along projections
Nuclear magnetic resonance
Magnetic resonance spectroscopy
Number of accumulation
Point resolved spectroscopy sequence
Transversal relaxation time constant
Variable power and optimised relaxation delays
We thank Dr. Peter Erhard for helpful comments on the manuscript. This work was supported by the Deutsche Forschungsgemeinschaft (DFG) in the framework of the priority programme ‘Antarctic Research with comparative investigations in Arctic ice areas’ (SPP 1158) by grants DR298/13-1 and BO2467/4-1.
Compliance with ethical standards
Conflict of interest
All authors declare that they have no conflicts of interest.
The manuscript does not contain animal or clinical studies, patient or volunteer data.
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