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O-(2-18F-fluoroethyl)-L-tyrosine (18F-FET) is an established tracer for brain tumour imaging. 18F-FET kinetics in gliomas appear to have potential for tumour grading, but the mechanisms remain unclear. The aim of this study was to explore the relationship between regional cerebral blood flow (rCBF) as measured by arterial spin labelling MRI and the kinetic behaviour of 18F-FET PET in cerebral gliomas.Twenty patients with cerebral gliomas were investigated using arterial spin labelling MRI and dynamic 18F-FET PET. Time–activity curves (TACs) of 18F-FET uptake were analysed in 33 different tumour regions. The slopes of TAC during the early (0–5 min; slopeup) and late phases of tracer uptake (17–50 min; slopedown) were fitted using linear regression lines. In addition, TACs of each lesion were assigned to different curve patterns. Furthermore, we calculated tumour-to-brain ratios of 18F-FET uptake. The relationship between 18F-FET parameters and rCBF was determined.18F-FET uptake in the early phase (slopeup) showed a significant correlation with rCBF (r=0.4; P=0.02). In contrast, both slopedown and TAC patterns showed no significant correlation with rCBF. Furthermore, a significant correlation was found between rCBF and tumour-to-brain ratio (r=0.53; P=0.002).There is a relationship between rCBF and 18F-FET uptake in cerebral gliomas in the initial uptake phase, but the kinetic behaviour of 18F-FET uptake in the late phase is not significantly influenced by rCBF. Thus, the differential kinetic pattern of 18F-FET uptake in high-grade and low-grade gliomas appears to be determined by factors other than rCBF.