Biodistribution and Radiation Dosimetry of the

Whole-body radiation dosimetry of 11C-raclopride was per-formed in healthy human volunteers. Methods: Subjects (n 5 6) were scanned with PET. Subjects received single-bolus injections of 11C-raclopride (S-(2)-3,5-dichloro-N-[(1-ethyl-2-pyrrolidinyl)]methyl-2-hydroxy-6-methoxybenzamide) (533 6 104 MBq) and were scanned for approximately 110 min with a 2-dimensional whole-body protocol. Regions of interest were placed over all visually identifiable organs and time–activity curves were generated. Residence times were computed as the area under the curve of the time–activity curves, normalized to injected activities and standard values of organ volumes. Absorbed doses were computed according to theMIRD schema withMIRDOSE3.1 software.Results:Organswith the highest ra-diation burden were gallbladder wall, small intestine, liver, and urinary bladder wall. Conclusion: On the basis of the estimated absorbed dose, themaximum allowable single study dose under U.S. federal regulations for studies performed under Radiatio