The research discussed in this article aimed to characterize better the biodistribution, excretion and radiation dosimetry of the single photon emission computed tomography (SPECT) D2 Dopamine receptor radioligand [123I]IBF. Following administration of 111 +/- 12 MBq [123I]IBF, seven healthy human subjects were scanned serially with a whole body imager over a 48-h period. Transmission images were obtained with a scanning line source for attenuation correction of the emission images. Urine was collected for 48 h to measure the fraction of activity voided by the renal system. Radiation absorbed dose estimates were performed using biokinetic modeling and the Medical Internal Radiation Dose (MIRD) schema. Highest absorbed doses were to the kidney (0.13 +/- 0.02 mGy/MBq) and urinary bladder wall (0.11 +/- 0.01 mGy/MBq). The effective dose equivalent was 0.041 +/- 0.005 mSv/MBq. Peak brain uptake represented 8% of the injected activity. Rapid urinary excretion minimized the absorbed dose to most tissues. The mean cumulative urinary excretion fraction was 69%. Thus [123I]IBF is a promising SPECT agent for imaging the D2 dopamine receptor in humans with high brain uptake and favorable dosimetry.
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