Whole-body biodistribution, radiation absorbed dose and brain SPECT imaging with iodine-123-beta-CIT in healthy human subjects.
SPECT imaging with 123I-labeled methyl 3 beta-(4-iodophenyl)tropane-2 beta-carboxylate ([123I]beta-CIT) in nonhuman primates has shown brain striatal activity, which primarily reflects binding to the dopamine transporter. The biodistribution and calculated radiation-absorbed doses of [123I]beta-CIT administered to eight healthy subjects were measured with attention to the accurate determination of organ time-activity data.


METHODS
Whole-body transmission images were obtained with a scanning line source for attenuation correction of the emission images. Following administration of 92.5 +/- 22.2 MBq (2.5 +/- 0.6 mCi) of [123I]beta-CIT, subjects were imaged with a whole-body imager every 30 min for 3 hr, every 60 min for the next 3 hr and at 12, 24 and 48 hr postinjection. Regional body conjugate counts were converted to microcuries of activity, with a calibration factor determined in a separate experiment using a distributed source of 123I.


RESULTS
The peak brain uptake represented 14% of the injected dose, with 2% of the activity approximately overlying the striatal region. Highest radiation-absorbed doses were to the lung (0.1 mGy/MBq, 0.38 rads/mCi), liver (0.087 mGy/MBq, 0.32 rads/mCi) and lower large intestine (0.053 mGy/MBq, 0.20 rads/mCi).


CONCLUSIONS
Iodine-123-beta-CIT is a promising SPECT agent for imaging of the dopamine transporter in humans with favorable dosimetry and high brain uptake.
Seibyl
J P
JP
Department of Psychiatry, Yale University School of Medicine, New Haven, Connecticut.
Wallace
E
E
Smith
E O
EO
Stabin
M
M
Baldwin
R M
RM
Zoghbi
S
S
Zea-Ponce
Y
Y
Gao
Y
Y
Zhang
W Y
WY
Neumeyer
J L
JL
D000328:Adult; D001921:Brain / Q000000981:diagnostic imaging* / Q000378:metabolism*; D003042:Cocaine / Q000031:analogs & derivatives* / Q000493:pharmacokinetics; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes / Q000493:pharmacokinetics*; D008297:Male; D011829:Radiation Dosage; D014018:Tissue Distribution; D015899:Tomography, Emission-Computed, Single-Photon
D007457:Iodine Radioisotopes; C069723:2beta-carbomethoxy-3beta-(4-iodophenyl)tropane; D003042:Cocaine