QUANTIFICATION OF PHOSPHORUS METABOLITES IN HUMAN CALF MUSCLE AND SOFT-TISSUE TUMORS FROM LOCALIZED MR SPECTRA ACQUIRED USING SURFACE COILS

Metabolite concentrations determined from MR spectra provide more spec ific information than peak area ratios. This paper presents a method o f quantification that allows metabolite concentrations to be determine d from in vivo P-31 MR spectra acquired using a surface coil and ISIS localization. Corrections for the effects of B-1 field inhomogeneity p roduced by surface coils are based on a measured and calibrated spatia l sensitivity field map for the coil. Account is taken of imperfection s in pulse performance, coil loading effects and relaxation effects, t he latter making use of published metabolite relaxation times. The tec hnique is demonstrated on model solutions. The concentrations of the m ain P-31 metabolites in normal human calf muscle measured using this m ethod are [PCr] = 26.9+/-4.1 mM; [Pi] = 3.6+/-1.2 mM; [NTP] = 6.8+/-1. 8 mM. Quantification of spectra acquired from soft-tissue tumours in p atients both pre- and post-treatment showed that changes in metabolite concentrations are more sensitive to metabolic changes than changes i n peak area ratios.