Absorbed Dose Estimates in Positron Emission Tomography Studies Based on the Administration of ¹⁸F-Labeled Radiopharmaceuticals

Absorbed doses were estimated after intravenous administration of ¹⁸F-labeled radiopharmaceuticals in Positron Emission Tomography (PET) studies. These radiopharmaceuticals_; [^,8F]-2-Fiuoro-2-Deoxy-D-Glucose (FDG), 6-[¹⁸F]Fluoro-L-Dopa (FDOPA) and ^,8F-5-Fluorodcoxyuridine (FdUR), are used in clinical research at the Cyclotron and Radioisotope Center of Tohoku University. Radiopharmaceutical biokinetic values were measured in humans or extrapolated from animal experiments. Selective organ uptake and rapid clearance of activity from the blood were observed. High activity in the bladder contents of humans was found. Calculations were made by the MIRD method, modified to account for the differences in physique and organ mass between the Caucasian Reference Man and the Japanese one. The bladder wall receives the highest dose (more than 1.23x10 ¹ mGy/MBq) when any of these compounds arc administered. Other organs receiving high doses are the heart, brain and kidneys from FDG; the kidneys and pancreas from FDOPA, and the kidneys and small intestine from FdUR. These organs received absorbed doses of more than 2.7x10“ ² mGy/MBq. Effective dose equivalents of 2.4xl0”², 2.6xl0~² and 3.3xl0^-2 mSv/MBq were estimated in the intravenous administration of ^l8F-FDG, ^1KF-FDOPA and ^!8F-FdUR, respectively.