Intracranial tumors in children: small single-voxel proton MR spectroscopy using short- and long-echo sequences

We report preliminary experience using single-voxel, proton MR spectroscopy (MRS) employing small voxels of interest, in combination with short and long echo-time protocols, for the assessment of primary intracranial tumors in children. We examined 23 children with primary intracranial tumors detected by MRI, and 32 controls with similar ages, using MRS on a 1.5 T system. Localized single-voxel (3.7 +/- 1.3 cc) proton spectra were obtained with short-echo (2,000/18), stimulated-echo (STEAM) and long-echo (2,000/270) spin-echo (PRESS) protocols. All spectra were evaluated qualitatively; 10 tumor and 19 control spectra were processed for peak area quantification. Small voxels of interest were able to account for tissue heterogeneity. Combined acquisition of short- and long-echo spectra increased the number of detectable metabolites. The solid portion of all tumors exhibited reduced N-acetyl-aspartate (NAA), strong contribution from cholines (Cho) and inositols or glycine, minimal presence of total creatine (tCr), enhanced broad mobile lipid resonances and accumulated lactate. Calculated selected metabolite ratios of Cho/tCr and Cho/NAA were substantially increased from control values. The cystic portions of the masses showed only lipid and lactate peaks.