OUTLINE: Part I: Patients who are scheduled to have surgical resection of brain tumor undergo conventional magnetic resonance imaging (MRI), proton magnetic resonance spectroscopic imaging (1H-MRSI), and diffusion magnetic resonance imaging (DI) within 1 week before resection. Patients undergo conventional MRI within 72 hours after completion of surgical resection. Image characteristics of the resected tissue are correlated with histopathological measures. Part II: Patients who have clinical indications for increasing the dexamethasone dose are treated on part II of the study. Patients are stratified by status of steroid treatment (steroid naive vs prior steroid management). Patients undergo conventional MRI, 1H-MRSI, and DI within 2 days before and within 4-7 days after increasing the dexamethasone dose. Image characteristics on films taken before and after increasing the dexamethasone dose are compared.