Noninvasive estimation of human radiation dosimetry of 18F-FDG by whole-body small animal PET imaging in rats

Purpose: Small animal PET provides the biodistribution of administrated radiotracer in vivo and have a potential to contribute on dosimetry study. The aim of this study is to investigate the effect of region-of-interest (ROI)delineation in whole-body rat PET image toward non-invasive estimation of human dosimetry of 18F-FDG. Method: After administration of 18F-FDG (averaged 11.7 MBq), 3.5-h PET and 20-min CT scans were sequentially performed for three rats by Clairvivo PET/CT system. Seven source organs, and the remainder of the body, were studied to extrapolate %ID(t) and estimate time-integrated activity coefficients [kBq-h/MBq] in human. The mean absorbed dose in each target organ and the effective dose were estimated by MIRD method. Effects of ROIdefinitions on both extrapolated %ID(t) in human and estimated doses were also investigated by using (i) small ROIs of high uptake region and (ii) whole organ ROIs. Results: Averaged effective doses of 18F-FDG in human by using high-uptake and whole-organ ROIs were 27.8 +/- 6.54 and 19.3 +/- 2.72 mu Sv/MBq, respectively. Conclusion: The use of small animal PET scanner, which allows repeatedly PET scans, have a potential to contribute on the reduction of the number of experimental animals. However, the ways of ROI drawing influences on the estimated effective dose and safe-side ROI definition may be preferred.