The coline metabolite pattern detected by 1H HR MAS accurately discriminates between high and low human glioma grade.

In vivo 1H MRS has been widely used to identify the different metabolites present in brain tumors. However, due to the poor resolution of the in vivo spectra, it only allows the detection and the accurate quantification of very few. The HR-MAS (High Resolution Magie Angle Spinning) Magnetic Resonance Spectroscopy has proved to be a useful tool to overcome this problem. The purpose of this work is the study of the relative contributions of the main choline containing compounds (Cho, PC and GPC) to the total choline (tCho) signal and the evaluation of the potential role of these data in the discrimination betwecn low and high grade glioma. Human biopsies of grade II (low grade) and grades III and IV (high grade) astrocytomas were obtained from the neurosurgery department at "La Paz" Hospital. The HR-MAS spectra of the rumor biopsies were acquired on a 500 MHz Bruker AVANCE Spectrometer, at 4°C and 4 kHz spinning rate. Data were acquired with a classical CPMG with an effective echo time of 144 ms. Metabolite assignments were confirmed by 2D-COSY. The relative contributions of Cho, GPC and PC to the tCho were calculated by fitting lorentzian peaks to the corresponding resonances. The statistical analysis was performed using SPSS (SPSS Inc., Chicago, Illinois). The HR-MAS spectra showed a very high resolution, allowing for the individuai analysis of Cho, PC and GPC. The PC/tCho and the GPC/tCho ratios were significantly different between low grade and high grade gliomas, but did not help to discriminate between grade IH and grade IV (Fig. Ib). Also, the scatter plot of all the data showed that no overlapping at all exists for these two ratios between low and high grade, which implies that no false positives would occur when using this variables as markers for diagnosis. We also calculated the tCho/Cr ratio, which is conventionally used in the in vivo spectra analysis since Cho, PC and GPC cannot be distinguished under these conditions. No statistically significant differences were found for the tCho/Cr ratio between low and high grade gliomas, indicating that the individual contributions of PC and GPC to the tCho, rather than the tCho itself, are the specific markers of tumor malignancy.