Radiation dosimetry and biodistribution of 11C-ABP688 measured in healthy volunteers.
BACKGROUND
In this study, we assessed the whole-body biodistribution and radiation dosimetry of the new glutamatergic ligand (11)C-ABP688. This ligand binds specifically to the metabotropic glutamatergic receptor of subtype 5 (mGluR5).


METHODS
The study included five healthy male volunteers aged 20-29 years. After intravenous injection of 240-260 MBq, a series of four to ten whole-body positron emission tomography/computed tomography scans were initiated, yielding 60-80 min of data. Residence times were then calculated in the relevant organs, and the software packages Mirdose and Olinda were used to calculate the absorbed radiation dose and the effective dose equivalent.


RESULTS
Of the excreted (11)C activity at 1 hour, approximately 80% were eliminated via the hepato-biliary pathway and 20% through the urinary tract. The absorbed dose (mGy/MBq) was highest in the liver (1.64 E (-2) +/- 5.08 E (-3)), gallbladder (8.13 E (-3) +/- 5.6 E (-3)), and kidneys (7.27 E (-3) +/- 2.79 E (-3)). The effective dose equivalent was 3.68 +/- 0.84 microSv/MBq. Brain uptake in the areas with high mGluR5 density was 2-3 (SUV). The agreement between the values obtained from Mirdose and the Olinda was excellent.


CONCLUSIONS
(11)C-ABP688 is a very promising ligand for the investigation of mGluR5 receptors in humans. Brain uptake is high and the effective dose equivalent so low that serial examinations in the same subject seem feasible.
Treyer
Valerie
V
PET Center, Division of Nuclear Medicine, University Hospital Zurich, Zurich, Switzerland.
Streffer
Johannes
J
Ametamey
Simon M
SM
Bettio
Andrea
A
Bläuenstein
Peter
P
Schmidt
Mark
M
Gasparini
Fabrizio
F
Fischer
Uta
U
Hock
Christoph
C
Buck
Alfred
A
D001921:Brain / Q000000981:diagnostic imaging / Q000378:metabolism; D002250:Carbon Radioisotopes / Q000493:pharmacokinetics*; D006801:Humans; D007700:Kinetics; D010091:Oximes / Q000493:pharmacokinetics*; D049268:Positron-Emission Tomography; D011725:Pyridines / Q000493:pharmacokinetics*; D011829:Radiation Dosage; D018094:Receptors, Metabotropic Glutamate / Q000037:antagonists & inhibitors; D012016:Reference Values; D014018:Tissue Distribution; D014057:Tomography, X-Ray Computed; D014916:Whole-Body Irradiation
C510950:3-(6-methylpyridin-2-ylethynyl)cyclohex-2-enone-O-methyloxime; D002250:Carbon Radioisotopes; D010091:Oximes; D011725:Pyridines; D018094:Receptors, Metabotropic Glutamate