18F-DOPA is a precursor of dopamine after the same metabolic pathways

18F-DOPA is a precursor of dopamine after the same metabolic pathways, including the synthesis of catecholamines. 18F-DOPA PET/CT has been initially proposed in the assessment of patients with movement disorders due to the uptake of 18F-dopa by the terminals of dopaminergic neurones and its conversion to 18F-dopamine by dopa decarboxylase, and subsequently to other dopamine metabolites (17). The uptake of dopamine precursors reflects the integrity of presynaptic dopaminergic receptors hence its deficiency has been shown to accurately reproduce the monoaminergic disturbances in Parkinson’s disease. 18F-DOPA PET is very accurate (sensitivities 90%-100% and specificities 91%) for differentiating Parkinson’s disease from other Parkinson-like entities in selected cases, in which a clinical diagnosis is challenging (18) (19). More recently 18F-DOPA have been most successful in the field of brain tumour imaging due to their favourable mechanism of uptake, that depends on the increased expression of the L-type amino acid transport system on tumour cells. This metabolic pathway is highly specific for cancer cells and largely independent of blood–brain barrier breakdown, resulting in excellent tumour-to-background contrast. Pathological amino acid uptake usually extends beyond ce-T1-W abnormalities and is more specific than T2-weighted (or FLAIR) hyper-intensities (20). The inclusion of amino acid PET tracers in the work-up of brain tumours complements and improves the diagnostic performances of conventional MRI in several settings, including biopsy targeting, prediction of anaplastic transformation, response assessment and treatment planning for both high-grade and low-grade gliomas.