Quantification of spectral signals

An accurate assessment of the metabolite or lipid content in skeletal musculature plays an important role for studying physiological and pathological aspects of lipid metabolism. In principle, quantitative results 

However, to obtain absolute concentrations of metabolites, it is necessary to analyse precisely the area under the resonance line of interest which is especially difficult for overlapping signals. In addition, a reliable calibration technique is needed to assess the correlation between the area under a resonance line and the absolute concentration of the metabolite in the tissue. 

In Section 5.1 usual strategies to obtain reliable calibration by external and internal references are reported. Section 5.2 presents techniques for analysing overlapping resonance lines with symmetric and well-defined lineshapes. Section 5.3 shows a more suitable approach for differentiation of IMCL and EMCL in the complex signal patterns of lipids in muscle spectra. 

To obtain absolute concentrations of metabolites, calibration techniques are necessary. For this purpose an external calibration compound of known concentration can be measured to which the metabolite signals are referenced. Another possibility is the use of spectral signals from a tissue compound with known concentration serving as internal reference. 

For calibration with an external reference, a sample with known concentration of the compound of interest is positioned outside the examined object, but inside the receiver coil. The desired metabolite concentration in the tissue can be calculated from the known concentration in the external reference by 

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