OBJECTIVES: I. Determine whether proton magnetic resonance spectroscopic imaging (1H-MRSI) and diffusion magnetic resonance imaging (DI) measures of glioma cell burden correlate with histopathologically measured cell counts in glioma patients who are scheduled to undergo surgical resection. II. Determine whether 1H-MRSI and DI measures of glioma cell burden are invariant over the short term (1 week) as steroid dose is increased in these patients.