Human Biodistribution and Dosimetry of the D2/3 Agonist 11C-N-Propylnorapomorphine (11C-NPA) Determined from PET

We measured the whole-body distribution of intravenously in-jected 11C-N-propylnorapomorphine (11C-NPA), a dopamine ag-onist PET tracer, in human subjects and determined the resulting absorbed radiation doses. Methods: Six subjects (3 women, 3 men) were injected with 11C-NPA (nominal dose, 370 MBq). A total of 9 consecutive whole-body PET scans were obtained for each subject. In addition, time–activity curves for 12 organs were determined, and residence times were computed for each subject. Dosimetry was determined for the various body or-gans and the whole body. Results: The average NPA whole-body radiation dose was 3.17 · 1023 mSv per MBq of injected 11C-NPA. The organ receiving the highest dose was the gallbladder wall, with an average of 2.81 · 1022 mSvMBq21. Conclusion: On the basis of averaged dosimetry results, an ad-ministration of less than 1,780 MBq (,48 mCi) of 11C-NPA yields an organ dose of under 50 mSv (5 rem) to all organs