The limited chemical shift dispersion of in uiuo "P NMR spectra obtained at the relatively low field strengths used for human applications is the cause of poor spectral resolution. This makes it di8fidt to obtain accurate quantitative information from overlapping resonances, and interesting resonances may be obscured. At 1.5 T unresolved 'H-3'P couplings contribute significantly to the liewidth of in uiuo "P NMR resonances. Therefore, proton decoupliig can improve spectral resolution substantially, resulting in better resolved resonances and more reliable quantitative information. In this work it is shown that well resolved resonances of glycerophosphocholine, glycerophosphoethanolamine and phosphoethanolamine are obtained in ' H decoupled "P N M R spectra of human muscle, brain, and liver. In spectra of the human heart it has been possible to resolve the myocardial Pi signal from the signals of 2,3-diphosphoglycerate from blood. With surface coils it is dficult to achieve broadband decoupliig over the entire sensitive region of the coil by using conventional decoupling sequences. This problem has been overcome by applying a train of frequency modulated inversion pulses to achieve proper decoupliig despite B, inhomogeneity. Broadband 'H decoupling of "P NMR spectra was possible without exceeding specific absorption rate guidelines.

Experimental procedures for obtaining localized 31P NMR spectra of humans by means of the ISIS sequence are discussed in detail. The technique is optimized for use with volume coils and with surface coils in order to measure localized 31P NMR spectra of different tissues and organs. Selective frequency-modulated (FM) inversion and excitation pulses are applied for optimal inversion or excitation despite B1 inhomogeneity. Pulse imperfection may lead to spurious signal contributions from outside the selected volume; this contamination is reduced by using long pulse intervals, by properly ordering the ISIS acquisitions, and by using FM excitation pulses. Simultaneous measurement of multiple volumes was implemented by including an additional selective inversion pulse, and an extension of the ISIS addition/subtraction scheme. Localized T1 measurements with surface coils are implemented by using a B1-insensitive inversion pulse in the inversion recovery sequence. The quantitative reproducibility of localized 31P NMR spectra was verified. Absolute metabolite concentration can be determined after a suitable calibration of the 31P NMR spectrum. Localized shimming is required to obtain localized 31P NMR spectra of excellent spectral resolution. This is done by monitoring the 1H NMR signal from water by a single-shot localization technique. The techniques discussed can be applied to obtain spectra of brain, liver, heart, and other organs. 31P NMR spectra of intracranial tumors demonstrate its applicability in the examination of patients.

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