QUANTITATIVE-EVALUATION OF NEUTRAL AMINO-ACID-TRANSPORT IN CEREBRAL GLIOMAS USING POSITRON EMISSION TOMOGRAPHY AND F-18 FLUOROPHENYLALANINE

To elucidate the mechanism of large neutral amino acid (LNAA) transpor t in cerebral gliomas and to evaluate the clinical usefulness of posit ron emission tomography (PET) with fluorine-18 fluorophenylalanine (F- 18-Phe), we examined 18 patients with cerebral glioma using dynamic PE T and F-18-Phe, By employing two-compartment model analysis, the influ x rate K-1, the efflux rate k(2) and the distribution volume (V-d) Of F-18-Phe were estimated in tumour tissue and contralateral normal grey matter. F-18-Phe showed increased accumulation in tumour tissue regar dless of the grade of malignancy in all patients, The rate of uptake o f F-18-Phe in high-grade glioma was significantly higher than in low-g rade glioma (P < 0.05). However, it was difficult to evaluate the tumo ur grade only from the F-18-Phe accumulation in individual cases. Valu es of K-1 and V-d were significantly increased in the tumour tissue. T he K-1 value of the tumour tissue tended to decrease with increasing L NAA concentration in plasma, Therefore, influx of F-18-Phe into tumour tissue is mainly related to the carrier-mediated active transport. It is concluded that PET with F-18-Phe is of clinical value for tumour d etection rather than assessment of tumour malignancy.