Long-term positron emission tomography evaluation of slowly progressive gliomas.

Non-invasive positron emission tomography (PET) was performed to identify changes in blood flow and metabolism, specific to early stages of tumour occurrence or recurrence. 2 patients with slowly progressive gliomas from early to late stages of tumour development were analysed by serial PET measurements of circulation and metabolism using 15O-gas and 18F-fluorodeoxyglucose. PET revealed a persistent depression of oxygen metabolism, as indicated by the regional oxygen extraction fraction or metabolic rate of oxygen, in the regions where tumours were later found. Abnormal blood flow and metabolism may precede the morphological changes detected by computed tomography (CT) in patients with gliomas.