Localized 2D J-resolved 1H MR spectroscopy of human brain tumors in vivo.

Application of two-dimensional (2D) J-resolved MR spectroscopy, fully localized in three dimensions to monitor the metabolites in human brain tumors in vivo on a whole body MR scanner is presented. A modified PRESS sequence with [90 degrees - 180 degrees - t1/2 - 180 degrees - t1/ 2-acquisition] was used for voxel localization (2D J point-resolved spectroscopy [PRESS]); chemical shift selective (CHESS) sequence was used for suppression of water. The incremental delay (t1/2) added to the intervals before and after the last slice-selective 180 degrees RF pulse allowed the monitoring of the J-evolution in a localized 2D NMR spectrum. The addition of the second frequency dimension in 2D J-resolved spectroscopy to encode the indirect spin-spin coupling allowed the visualization of lactate peaks not observed in the 1D MR spectrum because of severe overlap with lipid peaks. 2D spectra of a two-layer phantom with 100 mM alanine and corn oil and also from three patients with tumors are presented here. The 2D spectra show that the J-coupled lactate peaks could be separated even when the lipids peaks severely overlap.