Resolution enhancement in in vivo NMR spectroscopy: detection of intermolecular zero-quantum coherences.
Intermolecular zero-quantum coherences are insensitive to magnetic field inhomogeneities. For this reason we have applied the HOMOGENIZED sequence [Vathyam et al., Science 272 (1996) 92] to phantoms containing metabolites at low concentrations, phantoms with air inclusions, an intact grape, and the head of a rat in vivo at 750 MHz. In the 1H-spectra, the water signal is efficiently suppressed and line broadening due to susceptibility gradients is effectively removed along the indirectly detected dimension. We have obtained a 1H-spectrum of a 2.5 mM solution of gamma-aminobutyric acid in 12 min scan time. In the phantom with air inclusions a reduction of line widths from 0.48 ppm in the direct dimension to 0.07 ppm in the indirect dimension was observed, while in a deshimmed grape the reduction was from 1.4 to 0.07 ppm. In a spectrum of the grape we were able to resolve glucose resonances at 0.3 ppm from the water in 6 min scan time. J-coupling information was partly retained. In the in vivo spectra of the rat brain five major metabolites were observed.
Faber
Cornelius
C
Physikalisches Institut, Universität Würzburg, Am Hubland, Würzburg, D-97074, Germany. faber@physik.uni-wuerzburg.de
Pracht
Eberhard
E
Haase
Axel
A
D000388:Air; D000818:Animals; D001921:Brain / Q000378:metabolism*; D005260:Female; D005947:Glucose / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D019047:Phantoms, Imaging; D051381:Rats; D027843:Vitis; D005680:gamma-Aminobutyric Acid / Q000737:chemistry
D005680:gamma-Aminobutyric Acid; D005947:Glucose