Visualization of the gall bladder on F-18 FDOPA PET imaging: A potential pitfall

The ability to label dihydroxyphenylalanine (DOPA) with the positron-emitting isotope F-18 has helped to identify the deficiency of dopamine synthesis and storage within presynaptic striatal nerve terminals. FDOPA PET, therefore, has been used in the diagnosis of early Parkinson disease and the differentiation of a parkinsonian syndrome from other movement disorders. Furthermore, the uptake and metabolism of amino acids by tumors makes F-18 FDOPA PET a suitable alternative to F-18 FDG PET imaging, although the experience in this situation is very limited. Because the main indication for FDOPA PET imaging in the past has been the brain in suspected Parkinson disease, there is a paucity of information on normal whole-body distribution of FDOPA. The author reports a case in which intense uptake of the tracer in the gall bladder mimicked a large liver metastasis from a neuroendocrine primary, but correlative CT and knowledge of the normal biliary route of excretion of the radiopharmaceutical helped to avoid a diagnostic pitfall.