The purpose of this study was to examine muscle glycogen recovery with glucose feeding (GF) compared with fructose feeding (FF) during the first 8 h after partial glycogen depletion using 13C-nuclear magnetic resonance (NMR) on a clinical 1.5-TNMR system. After measurement of the glycogen concentration of the vastus lateralis (VL) muscle in seven male subjects, glycogen stores of the VL were depleted by bicycle exercise. During 8 h after completion of exercise, subjects were orally given either GF or FF while the glycogen content of the VL was monitored by 13C-NMR spectroscopy every second hour. The muscular glycogen concentration was expressed as percentage of the glycogen concentration measured before exercise. The glycogen recovery rate during GF (4.2 +/- 0.2%/h) was significantly higher (P < 0.05) compared with values during FF (2.2 +/- 0.3%/h). This study shows that 1) muscle glycogen levels are perceptible by 13 C-NMR spectroscopy at 1.5 T and 2) the glycogen restoration rate is higher after GF compared with after FF.

The authors investigated the feasibility of a multisection proton magnetic resonance (MR) spectroscopic imaging technique for the acquisition of metabolic information in the human prostate. Multisection MR spectroscopic imaging was performed of a citrate phantom and of the prostates of eight adult volunteers. High-quality proton MR spectra and citrate metabolite maps of the prostate were obtained with this method.

Glycogen synthesis rate showed a strong correlation with whole body glucose uptake during the clamp (r = 0.93, P < 0.01). With the use of 13C MRS, total muscular glucose content could be determined in vivo, and showed a positive, linear correlation with glycogen synthesis rate (r = 0.85, P < 0.01). 13C MRS provides important information regarding in vivo insulin action. Preliminary results indicate that the glycogen synthesis rate improves after treatment with troglitazone.

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For patient safety in human 1H decoupled 13C-MRS, it is absolutely necessary to evaluate the specific RF absorption rate (SAR) of the tissue exposed to 1H frequency irradiation. With the use of surface coils, the local SAR at the body surface is of most concern due to the inherent RF field inhomogeneity. An empirical procedure to spatially calibrate the decoupler power level and to evaluate the local SAR at the body surface is described. For head, liver, muscle gastrocnemius, and muscle vastus lateralis, the SAR at the body surface was estimated for an 1H/13C double surface coil setup. Optimized duty cycle values obtained with this procedure show that broad-band 1H-decoupled 13C-MR spectroscopy is clinically feasible at 1.5 T for such a coil configuration within safety guidelines.