Whole-body biodistribution and dosimetry of the dopamine transporter radioligand ¹⁸F-FE-PE2I in human subjects

Abstract

¹⁸F-(E)-N-(3-iodoprop-2-enyl)-2β-carbofluoroethoxy-3β-(4'-methyl-phenyl) nortropane (¹⁸F-FE-PE2I) was recently developed and has shown adequate affinity and high selectivity for the dopamine transporter (DAT). Previous studies have shown promising results for ¹⁸F-FE-PE2I as a suitable radioligand for DAT-imaging. In this study, we investigate the whole body biodistribution and dosimetry of ¹⁸F-FE-PE2I in healthy volunteers to support the utility of it as a suitable positron emission tomography (PET) imaging agent for the DAT. Methods: Five healthy volunteers were given a mean activity of 2.5 MBq/kg and three PET scans, head to thigh, were performed immediately after injection followed by four whole body positron emission tomography/computed tomography (PET/CT) scans between 0.5 and 6 hours after injection. Blood samples were drawn in connection to the whole-body scans and all urine was collected until 6 hours after injection. Volumes of interest (VOIs) were delineated around 17 organs on all images and the areas under the time-activity curves were calculated to obtain the total number of decays in the organs. The absorbed doses to organs and the effective dose were calculated using the software IDAC. Results: The highest activity concentration was observed in the liver (0.9-1.2 %IA/100g) up to 30 minutes after injection. At later time points the highest concentration was seen in the gallbladder (1.1-0.1 %IA/100g). The activity excreted with urine ranged between 23% and 34%, with a mean of 28%. The urinary bladder received the highest absorbed dose (120 µGy/MBq), followed by the liver (40 µGy/MBq). The effective dose was 22 µSv/MBq (range 18-25 µSv/MBq), resulting in an effective dose of 4.4 mSv for an administered activity of 200 MBq. Conclusion: The effective dose is within the same order of magnitude as other commonly used PET imaging agents as well as DAT agents. The reasonable effective dose, together with the previously reported favorable characteristics for DAT imaging and quantification, indicates that ¹⁸F-FE-PE2I is a suitable radioligand for DAT-imaging.