The present study used PET with the third-generation ligand (S)-N,N-diethyl-9-(2-18F-fluoroethyl)-5-methoxy-2,3,4,9-tetrahydro-1H-carbazole-4-carboxamide (18F-GE-180) [8, 9] for the translocator protein (TSPO) to test the hypothesis that long-term immunosuppression with CNI in liver-transplanted patients is associated with reduced TSPO availability in the brain, indicating CNI-associated suppression of microglial activity, which in turn is associated with cognitive impairment. This evidence concerns the gene TSPO and Cognitive impairment.