Biodistribution considerations on 18F-DOPA PET/CT

1090 Objectives 18F-DOPA PET/CT is increasingly being used in the detection and management of neuroendocrine tumours (NETs). The aim of the study was to evaluate the biodistribution pattern and normal variants of 18F-DOPA in a cohort of patients with NETs using a semiquantitative analysis based on SUV max. Methods 107 consecutive patients (53 M, 54 F, range 9-85 years) who performed 18F-DOPA PET/CT were evaluated. All patients received an i.v. injection of a fixed dose of 185MBq of 18F-DOPA (without pre-treatment with carbidopa) and 1 hour later a whole-body acquisition was performed. Cytohistological findings in positive scans and clinical, laboratory and imaging follow-up (median 16 months) in the negative ones were considered as gold standard. The biodistribution of 18F-DOPA in both negative (32) and positive (75) scans was evaluated by a semiquantitative SUV max analysis considering the mean, median, SD and range of the SUVmax. Results The physiological biodistribution in the basal ganglia and liver parenchyma showed no variability between the two groups. The uptake in the pancreas, particularly the uncinate process (mean SUV max 5.67 range 2.9-14.1) and adrenals (mean SUV max 1.92, range: 0.7-4.3) was very variable in both groups . The Mann-Whitney test showed no significant variations between positive and negative scans. Also excretory organs (gallbladder, bowel, kidneys and urinary bladder) showed a wide variability of uptake. Conclusions A large variability of the physiologic 18F-DOPA uptake was seen in the pancreas especially in the uncinate process, in the adrenals and in some excretory organs. A good knowledge of the biodistribution of 18F-DOPA is mandatory in order to avoid misinterpretations of 18F-DOPA PET/CT scans