Magnetic Resonance Spectroscopy for Evaluation of Brain Glioma Extent

Introduction. Based on the long observations, gliomas recur predominantly within 1 centimeter of the resection margin. This is mainly due to the fact that at the time of surgical removal, cells from the core of the tumor have already invaded the peritumoral area that appears unchanged on structural magnetic resonance (MR) images. MR spectroscopy provides a noninvasive assessment of tumor metabolism with which the concentration of N-acetylaspartate (NAA), choline (Cho), creatine (Cr), lactate and lipid (LL), myo-inositol (MI) can be determined. Aim of the study. The purpose of this study was to evaluate the neurometabolites ratios as an indicator of the glial brain tumors infiltration into the surrounding tissue. Materials and methods. MR spectroscopy was performed in 54 patients with histologically confirmed brain glioma. Patients were divided into two groups based on the time of MR examination performed: before and after therapy. Regions of interest (ROIs) were placed in the tumor centre, the perifocal edema zone, the distant and contralateral normal-appearing white matter. Mean ratios of NAA/Cr, Cho/Cr, MI/Cr, LL/Cr were calculated in each ROIs. Results. In the both groups the Cho/Cr ratios were significantly elevated in the tumor and the edema zone; the NAA/Cr ratios were significantly reduced in the tumor; the LL/Cr ratios were significantly elevated in the tumor and the edema compared with the contralateral hemisphere. In the second group the Cho/Cr and LL/Cr ratios in the edema zone was significantly lower than in the tumor and significantly higher than in the distant white matter; the Cho/Cr, MI/Cr and LL/Cr ratios in the tumor were significantly higher than in the distant white matter. Conclusions. The analysis of spatial distribution of metabolites ratios by MR spectroscopy helps to discriminate among tumor and normal tissues, offering information not available with structural MR. LL/Cr ratios may have the superior implications in the detecting of glial tumors extent. Metabolic changes in the peritumoral area demonstrated by MR spectroscopy can assist in choosing a biopsy target for brain gliomas and in planning of surgical removal or radiation therapy.