Positron Emission Tomography Using Fluorothymidine F 18 in Finding Recurrent Disease in Patients With Gliomas

DISEASE CHARACTERISTICS: * Radiological or established histological diagnosis of glioma * WHO grade 2-4 disease * Presence of a new or enlarging enhancing lesion on gadolinium-enhanced MRI after prior radiotherapy * Differentiation of recurrent tumor from radiation necrosis is not possible * No clinically significant signs of uncal herniation, including any of the following: * Acute pupillary enlargement * Rapidly developing (i.e., over hours) motor changes * Rapidly decreasing level of consciousness PATIENT CHARACTERISTICS: * Platelet count ≥ 75,000/mm\^3 * WBC ≥ 3,000/mm\^3 * Gamma-glutamyl-transferase ≤ 5 times upper limit of normal (ULN) * Absolute neutrophil count ≥ 1,500/mm\^3 * Hemoglobin ≥ 10 g/dL * SGOT and SGPT ≤ 2 times ULN * Alkaline phosphatase ≤ 2 times ULN * Lactic dehydrogenase ≤ 2 times ULN * Direct and total bilirubin normal * Amylase normal * Haptoglobin normal * Serum electrolytes normal * CBC with platelets normal * PT, PTT normal * BUN and creatinine normal * Not pregnant or lactating * Urinalysis normal * Negative pregnancy test * Female patients must be postmenopausal for ≥ 1 year or surgically sterile, or on 1 of the following methods of birth control for ≥ 1 month: IUD, oral contraceptives, Depo-Provera, or Norplant * These criteria can be waived at the discretion of the investigator if the patient's intracranial tumor is considered life threatening and the 1-month wait required is not in the best interest of the patient * No known allergic or hypersensitivity reactions to previously administered radiopharmaceuticals * No known HIV positivity * Not requiring monitored anesthesia for positron emission tomography scanning PRIOR CONCURRENT THERAPY: * Concurrent biopsy or neurosurgical procedure for diagnostic and/or therapeutic purposes for this cancer allowed * Concurrent surgery for this cancer allowed