HUMAN BIODISTRIBUTION AND DOSIMETRY OF THE SPECT D-2 DOPAMINE-RECEPTOR RADIOLIGAND [I-123] IBF

The research discussed in this article aimed to characterize better th e biodistribution, excretion and radiation dosimetry of the single pho ton emission computed tomography (SPECT) D-2 Dopamine receptor radioli gand [I-123]IBF. Following administration of 111 +/- 12 MBq [I-123]IBF , seven healthy human subjects were scanned serially with a whole body imager over a 48-h period. Transmission images were obtained with a s canning line source for attenuation correction of the emission images. Urine was collected for 48 h to measure the fraction of activity void ed by the renal system. Radiation absorbed dose estimates were perform ed 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 effect ive dose equivalent was 0.041 +/- 0.005 mSv/MBq. Peak brain uptake rep resented 8% of the injected activity. Rapid urinary excretion minimize d the absorbed dose to most tissues. The mean cumulative urinary excre tion fraction was 69%. Thus [I-123]IBF is a promising SPECT agent for imaging the D-2 dopamine receptor in humans with high brain uptake and favorable dosimetry.