3D RINEPT {1H}-31P CSI: a feasible approach for the study of membrane turnover in the human brain.

A fast, full 3D elliptical k-space encoding phosphorous-31 ((31)P) chemical shift imaging sequence, incorporating heteronuclear polarization transfer editing (RINEPT), was established. RINEPT literally requires simultaneous pulses at the frequencies of both the sensitive and the insensitive nuclei, but only a few MR imaging systems feature a second independent transmit channel. In this study, possible signal degradation of a sequential sequence design on systems featuring a single transmit channel was investigated with spin density matrix calculations and phantom measurements. In addition, metabolite signal intensities were determined in vivo as a function of echo and repetition times. The results enable optimization of the signal-to-noise ratio of one or more metabolites of interest. The results convincingly show that the optimized RINEPT sequence is useful in clinical routine (31)PMRS protocols and provides spectra of excellent quality for the study of cell membrane phospholipid turnover in the human brain even at a low field strength of 1.5T. The 3D sequence design allows covering the whole brain in a single measurement, while scan times are compliant with clinical routine protocols.

Metabolic imaging of atrophic muscle tissue using appropriate markers in 1H and 31P NMR spectroscopy.

INTRODUCTION: The purpose of this feasibility study was to demonstrate non-invasive metabolic imaging of human muscular atrophy using significant changes of NMR signals that are related directly or indirectly to fiber necrosis. METHODS: Single-voxel (1)H NMR spectroscopy and two-dimensional (31)P spectroscopic imaging on a 1.5-T whole-body scanner were used for in vivo mapping of areas of muscle damage in two cases of differently localized and pronounced atrophy. Spectral patterns affiliated with severe and intermediate stages of degeneration were compared to data of healthy control tissue to derive appropriate metabolic markers related to lipid infiltration or high-energy (31)P metabolism. RESULTS: Reliable detection of atrophic tissue was achieved by the following parameters: (1) liposclerotic turnover is related to a drastic reduction in the water/lipid (1)H signal intensity ratio (up to a factor of 74 compared to adjacent healthy tissue); (2) the (31)P resonance of phosphocreatine (PCr) is an adequate marker for differentiation of intact myocells with high-energy metabolism from regions dominated by terminal fiber necrosis (PCr signal vanished nearly completely or intensity was reduced by a factor of 3 in affected muscles). Metabolic images based on this signal allowed accurate non-invasive localization of atrophic tissue. CONCLUSION: The molecular information provided by NMR spectroscopy--previously only used with poor localization in atrophy studies--enables access to both the myocell-specific high-energy metabolism and the result of lipid infiltration allowing non-invasive mapping of degenerate tissue. The ability to investigate the results of these advanced levels of atrophy would also be useful for studies of more subtle degrees of denervation.

Alcohol consumption significantly influences the MR signal of frontal choline-containing compounds.

The aim of this work was to evaluate the relationship between the amount of alcohol consumption of a group of social drinkers and the magnetic resonance spectroscopy signal of choline-containing compounds (Cho) in the frontal lobe. Two independent long echo (TE = 135 ms) (1)H MRSI studies, the first comprising 24 subjects with very low alcohol consumption, the second 18 subjects with a more widespread alcohol consumption were conducted. Significant correlations of Cho measures from frontal white matter and from the anterior cingulate gyrus with alcohol consumption in the last 90 days prior to the MR examination were found. Age, gender, and smoking did not show significant effects on the metabolite measures. Partialling out the effect of the voxel white matter content did not change the correlation of choline measures with alcohol consumption. The main conclusion from the repeated finding of a positive correlation of alcohol consumption and frontal Cho signals is that monitoring for alcohol consumption is mandatory in MRS studies where pathology depended Cho changes are hypothesized.