The study is designed to use infusion of a non-radioactive, naturally occurring isotope of glucose (13C) in patients undergoing surgical resection for a newly identified brain mass to obtain the metabolic phenotype of the tumor, and correlate it with the histopathological diagnosis. In each patient, 13C NMR spectral analysis of tumor extracts will be obtained after intraoperative infusion of \[U-13C\]glucose or \[1,2-13C\]glucose. Whenever feasible, patients will undergo 3 preoperative imaging studies - 18FDG-PET, diffusion tensor imaging with 1H-spectroscopy on 3T MR scanner, and ultra high resolution MR imaging on the 7T MR scanner. The results of these imaging studies will be correlated with the metabolic phenotype to generate a comprehensive non-invasive view of the tumor with the goal of identifying infiltrative, metabolically active tumor cells within the brain. In addition, a comprehensive molecular profile of the tumor will be obtained and enable a genotype-metabolic phenotype comparative analysis. Correlative Translational Research The investigators will obtain tumor tissue from each patient for comprehensive molecular analysis (array CGH, expression profiling, methylation profiling) which will be correlated with tumor histology, the metabolites identified by 1H-MR spectroscopy and the 13Cglucose metabolic profile. Patients will be followed at designated time points along their treatment course to obtain information about ongoing treatment and response, time to tumor progression and overall survival. These parameters will be used in correlational analysis with the metabolic phenotype.