An improved method for rapid and efficient radioiodination of iodine-123-IQNB.
The SPECT radioligand, 3-quinuclidinyl-4-[123I]iodobenzilate ([123I]IQNB), binds to muscarinic receptors and has generated interest as a potential agent for clinical SPECT. Unfortunately, cumbersome and inefficient radioiodination procedures have limited the practicality of [123I]IQNB SPECT imaging.


METHODS
We report a rapid (5 min) and simple radioiodination procedure for preparing [123I]IQNB from a tri-n-butylstannyl precursor in a no-carrier-added reaction that yields high specific activity with radiochemical yield exceeding 60%. The radiochemical purity of the final product exceeds 95%.


RESULTS
We have used this procedure to radioiodinate the four stereoisomers of [123I]IQNB. The procedure is highly reliable and reproducible. SPECT studies on a healthy human volunteer at 1, 2, 6 and 24 hr after injection of each of the four stereoisomers reveal expected differences in the kinetic and binding characteristics of the four stereoisomers. (R,S)-[123I]IQNB appears to be the SPECT agent of choice.


CONCLUSIONS
Radioiodination of [123I]IQNB from our tri-n-butylstannyl precursor is simpler, more efficient and less expensive than previous techniques. The potential exists for a "kit" which would be practical in a typical clinical setting.
Lee
K S
KS
Clinical Brain Disorders Branch, National Institute of Mental Health (NIMH), National Institutes of Health (NIH), Bethesda, Maryland, USA.
He
X S
XS
Jones
D W
DW
Coppola
R
R
Gorey
J G
JG
Knable
M B
MB
deCosta
B R
BR
Rice
K C
KC
Weinberger
D R
DR
D000328:Adult; D001921:Brain / Q000000981:diagnostic imaging; D006801:Humans; D007457:Iodine Radioisotopes; D007553:Isotope Labeling / Q000379:methods*; D008297:Male; D011813:Quinuclidinyl Benzilate / Q000031:analogs & derivatives / Q000737:chemistry; D013237:Stereoisomerism; D015899:Tomography, Emission-Computed, Single-Photon
D007457:Iodine Radioisotopes; D011813:Quinuclidinyl Benzilate; C040062:3-quinuclidinyl-4-iodobenzilate