[Phenylalanine transport in the living human brain by a dynamic PET of L-[2-18F]-fluorophenylalanine].

The transport kinetics of L-[2-18F]-Fluorophenylalanine in the human brain were studied in one normal subject and 6 patients with brain tumor using a dynamic positron emission tomography. The tracer kinetics from blood to brain were described by two compartment model with K1 (influx) and k2 (efflux). The rate constants in normal brain tissue and tumor tissue were K1 = 0.045 ml/g/min, k2 = 0.078 ml/g/min and K1 = 0.122 ml/g/min, k2 = 0.102 ml/g/min, respectively. The Michaelis-Menten constants (Kt and Tmax) for phenylalanine transport in the normal cortex were graphically estimated. The estimated Kt was 35 nmol/ml, whereas the Tmax varied with cerebral blood flow.