18F-choline PET/CT physiological distribution and pitfalls in image interpretation: experience in 80 patients with prostate cancer

OBJECTIVESF-choline positron emission tomography (PET)/computed tomography (CT) is an integral part in restaging of patients with prostate cancer (PC). The aim of this study was to describe the whole-body physiologic distribution of F-choline and to discuss some abnormal sites of uptake not related to PC we observed. MATERIALS AND METHODSEighty consecutive patients submitted to F-choline PET/CT imaging for primary staging or biochemical recurrence (prostate specific antigen rising) after treatment of PC was considered. Whole-body PET/CT was acquired approximately 40 min after F-choline injection. RESULTSWe observed physiological F-choline uptake in liver, pancreas, spleen, salivary and lachrymal glands and also, owing to renal excretion, in urinary tract. Other sites of less intense tracer uptake were bone marrow and intestines. We found abnormal and unexpected PET findings in 15 patients (18.7%), not owing to PC localizations. The majority of these findings were owing to inflammation (12 of 15); a case of low grade lymphoma was detected; two patients showed focal brain uptake of F-choline and were subsequently submitted to magnetic resonancein one a meningioma and in the other a low-grade brain tumour were diagnosed. CONCLUSIONAccurate knowledge of the biodistribution of F-choline is essential for the correct interpretation of PET/CT imaging. CT enables differentiation of physiological bowel activity and F-choline excretion in the ureters. In our series, F-choline uptake in benign pathological conditions mainly included sites of inflammation; nevertheless, accumulation in tumour deposits not because PC cannot be excluded, particularly in the brain, where correlative imaging with magnetic resonance is of the utmost importance.