ABSOLUTE QUANTITATIVE PROTON NMR-SPECTROSCOPY BASED ON THE AMPLITUDE OF THE LOCAL WATER SUPPRESSION PULSE - QUANTIFICATION OF BRAIN WATER AND METABOLITES

Quantification in localized proton NMR spectroscopy has been achieved by various methods in recent years. A new method for absolute quantifi cation is described in this paper. The method simultaneously rules out problems with B-1 field inhomogeneity and coil loading, utilizing a r elation between the locally optimized amplitude of a chemical shift se lective water suppression pulse and the acquired signal. Validity and feasibility of quantification using the method of the water suppressio n pulse is demonstrated. Brain water and cerebral metabolites have bee n quantified in a study of 12 healthy volunteers. Localized proton NMR spectra were obtained from a region of primarily white matter in the occipital lobe. The observable water content in the NMR spectra was 0. 685+/-0.025. The absolute metabolite concentrations were: [total choli ne] = 1.25+/-0.2 mM, [total creatine] = 6.71+/-0.59 mM and [NAA] = 9.1 5+/-0.74 mM. It is concluded that the quantification method is easily applied in vivo, and that the absolute concentrations obtained are sim ilar to results in other studies except those relying on assumptions o f the concentration of an internal reference. The advantage of the qua ntification method reported here is that it is independent of the assu mptions needed for other methods.