Brain kinetics of the new selective serotonin transporter tracer [(123)I]ADAM in healthy young adults

Recently, the tracer (123)I-2-([2-({dimethylamino}methyl)phenyl]thio)-5-iodophenylamine ([(123)I]ADAM) has been developed for selective imaging of serotonin transporters (SERTs) with single photon emission computed tomography (SPECT). The purpose of this study was to develop an [(123)I]ADAM SPECT protocol for clinical studies in young adults. METHODS: We examined the time course of [(123)I]ADAM binding to central SERTs in eight healthy young volunteers up to 6 h postinjection. RESULTS: We found that the time of peak-specific [(123)I]ADAM binding was highly variable among subjects, but specific binding in the SERT-rich (hypo)thalamus peaked within 5 h postinjection in all subjects. Moreover, in this brain area, binding ratios of specific to nonspecific binding did not significantly change between 3 and 6 h postinjection, and peaked 5 h postinjection. CONCLUSIONS: Five hours postinjection may be optimal for single-scan [(123)I]ADAM SPECT studies in humans, but more work is needed to assess the accuracy of the 5-h tissue ratio as a measure of SERT in the brain