Quantitative evaluation of neutral amino acid transport in cerebral gliomas using positron emission tomography and fluorine-18 fluorophenylalanine.

To elucidate the mechanism of large neutral amino acid (LNAA) transport in cerebral gliomas and to evaluate the clinical usefulness of positron emission tomography (PET) with fluorine-18 fluorophenylalanine (F-Phe), we examined 18 patients with cerebral glioma using dynamic PET andF-Phe. By employing two-compartment model analysis, the influx rate K, the efflux rate k and the distribution volume ( V) ofF-Phe were estimated in tumour tissue and contralateral normal grey matter.F-Phe showed increased accumulation in tumour tissue regardless of the grade of malignancy in all patients. The rate of uptake ofF-Phe in high-grade glioma was significantly higher than in low-grade glioma ( P <0.05). However, it was difficult to evaluate the tumour grade only from theF-Phe accumulation in individual cases. Values of K and V were significantly increased in the tumour tissue. The K value of the tumour tissue tended to decrease with increasing LNAA concentration in plasma. Therefore, influx ofF-Phe into tumour tissue is mainly related to the carrier-mediated active transport. It is concluded that PET withF-Phe is of clinical value for tumour detection rather than assessment of tumour malignancy. [ABSTRACT FROM AUTHOR]