Biodistribution and radiation dosimetry of the 18 kDa translocator protein (TSPO) radioligand [18F]FEDAA1106: a human whole-body PET study

Purpose [F-18]FEDAA1106 is a recently developed positron emission tomography (PET) radioligand for in vivo quantification of the 18 kDa translocator protein [TSPO or, as earlier called, the peripheral benzodiazepine receptor (PBR)]. TSPO imaging is expected to be useful for the clinical evaluation of neuroinflammatory diseases. The aim of this study was to provide dosimetry estimates for [F-18]FEDAA1106 based on human whole-body PET measurements. Methods PET scans were performed for a total of 6.6 h after the injection of 183.8 +/- 9.1 MBq of [F-18]FEDAA1106 in six healthy subjects. Regions of interest were drawn on coronal images. Estimates of the absorbed doses of radiation were calculated using the OLINDA software. Results Peak uptake was largest in lungs, followed by liver, small intestine, kidney, spleen and other organs. Peak values of the percent injected dose (%ID) at a time after radioligand injection were calculated for the lungs (27.1%ID at 0.2 h), liver (21.1%ID at 0.6 h), small intestine (10.4%ID at 6.3 h), kidney (4.9%ID at 1.8 h) and spleen (4.6%ID at 0.6 h). The largest absorbed dose was found in the spleen (0.12 mSv/MBq), followed by kidneys (0.094 mSv/MBq). The calculated mean effective dose was 0.036 mSv/MBq. Conclusion Based on the distribution and dose estimates, the estimated radiation burden of [F-18]FEDAA1106 is moderately higher than that of [F-18]fluorodeoxyglucose (FDG). In clinical studies, the administered activity of this radioligand ought to be adjusted in line with regional regulations. This result would be helpful for further clinical TSPO imaging studies.