%0 Journal Article %A Graeme J. O'Keefe %A Timothy H. Saunder %A Steven Ng %A Uwe Ackerman %A Henri J. Tochon-Danguy %A J. Gordon Chan %A Sylvia Gong %A Thomas Dyrks %A Stefanie Lindemann %A Gerhard Holl %A Ludger Dinkelborg %A Victor Villemagne %A Christopher C. Rowe %T Radiation Dosimetry of β-Amyloid Tracers 11C-PiB and 18F-BAY94-9172 %D 2009 %R 10.2967/jnumed.108.055756 %J Journal of Nuclear Medicine %P 309-315 %V 50 %N 2 %X β-Amyloid (Aβ) imaging has great potential to aid in the diagnosis of Alzheimer disease and the development of therapeutics. The radiation dosimetry of Aβ radioligands may influence their application; therefore, we calculated and compared the effective doses (EDs) of 11C-PiB and a new 18F-labeled ligand, 18F-BAY94-9172. Methods: Attenuation-corrected whole-body scans were performed at 0, 15, 30, 45, and 60 min after injection of 350 ± 28 MBq (mean ± SD) of 11C-PiB in 6 subjects and at 0, 20, 60, 120, and 180 min after injection of 319 ± 27 MBq of 18F-BAY94-9172 in 3 subjects. Coregistered CT was used to define volumes of interest (VOIs) on the PET images. The source organs were the brain, lungs, liver, kidneys, spleen, and vertebrae. The VOIs for the contents of the gallbladder, urinary bladder, lower large intestine, upper large intestine, and small intestine were also defined. Total activity in each organ at each time point was calculated by use of reference organ volumes. The resultant time–activity curves were fitted with constrained exponential fits, and cumulated activities were determined. A dynamic bladder voiding model was used. The OLINDA/EXM program was used to calculate the whole-body EDs from the acquired data. Results: For 11C-PiB, the highest absorbed doses were in the gallbladder wall (44.80 ± 29.30 μGy/MBq), urinary bladder wall (26.30 ± 8.50 μGy/MBq), liver (19.88 ± 3.58 μGy/MBq), and kidneys (12.92 ± 3.37 μGy/MBq). The ED was 5.29 ± 0.66 μSv/MBq. For 18F-BAY94-9172, the highest doses were also in the gallbladder wall (132.40 ± 43.40 μGy/MBq), urinary bladder wall (24.77 ± 7.36 μGy/MBq), and liver (39.07 ± 8.31 μGy/MBq). The ED was 14.67 ± 1.39 μSv/MBq. Conclusion: The estimated organ doses for 11C-PiB were comparable to those reported in earlier research. With the doses used in published studies (300–700 MBq), the EDs would range from 1.6 to 3.7 mSv. The ED of 18F-BAY94-9172 was 30% lower than that of 18F-FDG and, at the published dose of 300 MBq, would yield an ED of 4.4 mSv. The dosimetry of both Aβ radioligands is suitable for clinical and research applications. %U https://jnm.snmjournals.org/content/jnumed/50/2/309.full.pdf