Biodistribution and radiation dosimetry of [11C]raclopride in healthy volunteers.
OBJECTIVE
This study reports on the whole-body biodistribution and radiation dosimetry of [11C]raclopride, a dopamine D2 receptor antagonist.


METHODS
In three healthy male volunteers, whole-body scans were performed up to 2 h following i.v. injection of 320+/-65 MBq [11C]raclopride. Transmission scans (3 min per step, eight or nine steps according to the height of the subject) in 2D mode were used for subsequent attenuation correction of emission scans. Emission scans (1 min per step, eight or nine steps) were acquired over 2 h. Venous blood samples and urine were collected up to 2 h after injection of the radiotracer. For each subject, the percentage of injected activity measured in regions of interest over brain, intestine, lungs, kidneys and liver was fitted to a mono-exponential model, as an uptake phase followed by a mono-exponential washout, for urinary bladder to generate time-activity curves. Using the MIRD method, several source organs were considered in estimating residence time and mean effective radiation absorbed doses.


RESULTS
Blood pressure and ECG findings remained unchanged after tracer injection. The analysed blood and urine pharmacological parameters did not change significantly after [(11)C]raclopride injection. The primary routes of clearance were renal and intestinal. Ten minutes after injection, high activities were observed in the gall-bladder, kidneys and liver. High activity was observed in the gall-bladder during the whole study. The kidneys, urinary bladder wall, liver and gall-bladder received the highest absorbed doses. The average effective dose of [11C]raclopride was estimated to be 6.7+/-0.4 microSv/MBq.


CONCLUSIONS
The amount of [11C]raclopride required for adequate dopamine D2 receptor imaging results in an acceptable effective dose equivalent, permitting two or three repeated clinical PET imaging studies, with the injection of 222 MBq for each study.
Ribeiro
Maria-João
MJ
Service Hospitalier Frédéric Joliot, Département de Recherche Médicale, Direction des Sciences du Vivant, Commissariat à l'Energie Atomique, Orsay Cedex, France. ribeiro@shfj.cea.fr
Ricard
Marcel
M
Bourgeois
Sandrine
S
Lièvre
Marie-Angele
MA
Bottlaender
Michel
M
Gervais
Philippe
P
Dollé
Frédéric
F
Syrota
André
A
D000328:Adult; D001822:Body Burden; D001921:Brain / Q000000981:diagnostic imaging* / Q000378:metabolism*; D006801:Humans; D007275:Injections, Intravenous; D008297:Male; D008657:Metabolic Clearance Rate; D009928:Organ Specificity; D020891:Raclopride / Q000493:pharmacokinetics*; D011829:Radiation Dosage; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals / Q000008:administration & dosage / Q000493:pharmacokinetics; D012016:Reference Values; D014018:Tissue Distribution; D014915:Whole-Body Counting
D019275:Radiopharmaceuticals; D020891:Raclopride