Whole-body biodistribution and estimation of radiation-absorbed doses of the dopamine D₁ receptor radioligand ¹¹C-NNC 112 in humans

The present study estimated radiation-absorbed doses of the dopamine D ₁ receptor radioligand [¹¹C]((1)-8-chloro-5-(7- benzofuranyl)-7-hydroxy-3-methyl-2,3,4,5-tetrahydro-1H-3-benzazepine) (NNC 112) in humans, based on dynamic whole-body PET in healthy subjects. Methods: Whole-body PET was performed on 7 subjects after injection of 710 ± 85 MBq of ¹¹C-NNC 112. Fourteen frames were acquired for a total of 120 min in 7 segments of the body. Regions of interest were drawn on compressed planar images of source organs that could be identified. Radiation dose estimates were calculated from organ residence times using the OLINDA 1.0 program. Results: The organs with the highest radiation-absorbed doses were the gall-bladder, liver, lungs, kidneys, and urinary bladder wall. Biexponential fitting of mean bladder activity demonstrated that 15% of activity was excreted via the urine. With a 2.4-h voiding interval, the effective dose was 5.7 μSv/MBq (21.1 mrem/mCi). Conclusion: ¹¹C-NNC 112 displays a favorable radiation dose profile in humans and would allow multiple PET examinations per year to be performed on the same subject.