Aim: Evaluation of a peak at 3.55 ppm in a long echo time (TE) recognized as glycine (Gly) in the WHO grade II gliomas and central neurocytomas by means of 1H MRS.
Material and methods: Retrospective analysis of 19 patients with histopathologically confirmed WHO grade II glioma and 2 patients with central neurocytoma was conducted. 1H MRS (TE = 135 ms and TE = 144 ms) was performed with 1.5 T and 3.0 T scanners. Gly/Cr, Gly/Cho and Gly/NAA ratios were compared between the analysed groups. Additional analysis of a brain of 61 healthy volunteers was conducted.
Results: Glycine was distinguished in 12 out of 19 (63%) WHO grade II gliomas. Among those 12 WHO grade II gliomas only in 26% of a spectra Gly was recognized. In both central neurocytomas Gly was distinguished and in 43% of the spectra Gly was recognized. The ratio of Gly/Cr in central neurocytomas was higher than in WHO grade II gliomas (mean(CNC) 0.62 ± 0.18 vs. mean(WHO II) 0.37 ± 0.10; p < 0.001) but the ratio of Gly/Cho was lower (mean(CNC) 0.18 ± 0.04 vs. mean(WHO II) 0.24 ± 0.07; p < 0.001). There was no difference between analysed groups in terms of Gly/NAA ratio (mean(CNC) 0.36 ± 0.09 vs. mean(WHO II) 0.36 ± 0.14; p = NS). Only in 0.3% of the spectra of normal brain Gly was distinguished.
Conclusions: Glycine is found in WHO II grade gliomas as well as in central neurocytomas, but only in a part of a tumor volume. It is necessary to perform 1H MRS of the whole tumor volume to confirm/exclude the presence of glycine. Glycine in a normal brain can not be identified by means of conventional 1H MRS performed by means of 1.5 T or 3.0 T scanners.