DISEASE CHARACTERISTICS: - Pathologically confirmed glioblastoma multiforme - Newly diagnosed disease - Grade IV according to WHO criteria - Volume of residual tumor ≥ 4 cc after surgery on MRI with T1+ gadolinium-contrast - Scheduled to receive standard fractionated radiation therapy and temozolomide PATIENT CHARACTERISTICS: - Karnofsky performance status 60-100% - Not pregnant or nursing - Negative pregnancy test - Able to undergo MRI and use gadolinium-contrast agent, meeting the following criteria: - No claustrophobia - No metallic objects or implanted medical devices in the body (i.e., cardiac pacemaker, aneurysm clips, surgical clips, prostheses, artificial hearts, valves with steel parts, metal fragments, shrapnel, tattoos near the eye, or steel implants) - No sickle cell disease - No renal failure - No reduced renal function, as determined by glomerular filtration rate < 30 mL/min based on a serum creatinine level obtained within 28 days prior to study entry - No other co-exiting condition that in the judgment of the investigator might increase patient's risk - No concurrent serious systemic illness, including any of the following: - Uncontrolled intercurrent infection - Uncontrolled malignancy - Significant renal disease - Psychiatric or social situations that might impact the survival endpoint of the study or limit compliance with study requirements - No history of allergic reactions attributed to compounds of similar chemical or biologic composition to FMISO - Able to undergo PET or MRI (i.e., weight ≤ 350 lbs) - Able to tolerate 100% oxygen < 10 minutes (e.g., no history of chronic obstructive pulmonary disease) PRIOR CONCURRENT THERAPY: - See Disease Characteristics - No prior implanted radiotherapy or chemotherapy sources (i.e., wafers of polifeprosan 20 with carmustine) - Not scheduled to receive chemotherapy, immunotherapy, or biologic agent other than temozolomide, including any anti-tumor investigational agent