ROLE OF MAGNETIC RESONANCE SPECTROSCOPY IN GRADING OF BRAIN GLIOMAS.

Background: MR spectroscopic imaging (MRSI), or chemical shift imaging (CSI), is a newer noninvasive modality which provides biochemical information about different tissues that cannot be obtained by conventional MRI. It allows one to collect the spectral information from a volume consisting of many voxels where the ratios of peak areas or signal intensity of the metabolites are converted to an image and overlaid onto anatomic MR images, thus showing the quantitative or qualitative distribution of the metabolite within the brain area examined. Objective:To assess the role of MR Spectroscopy using various metabolite ratios in grading of brain gliomas into high grade and low grade. Methodology: 30 patients with gliomas evaluated on 1.5T conventional MR imaging followed by multivoxel proton MR spectroscopy, using Cho/Cr, Cho/NAA, NAA/Cr and lipid/lactate resonances. Observations: The mean Cho/Cr and Cho/NAA ratio was significantly elevated in high grade gliomas as compared to low grade gliomas. Higher ratios indicate increasing grade of malignancy. The presence of lactate and lipid resonancesindicates necrosis and appears to correlate with higher grades of malignancy. Conclusion: MR Spectroscopy evaluation of gliomas using Cho/Cr and Cho/NAA ratio when used in adjunct with conventional MRI findings can be near conclusive in grading of gliomas into high grade and low grade.