Serotonin Transporters in Dopamine Transporter Imaging: A Head-to-Head Comparison of Dopamine Transporter SPECT Radioligands 123I-FP-CIT and 123I-PE2I

Current SPECT radioligands available for in vivo imaging of the dopamine transporter (DAT) also show affinity for monoamine transporters other than DAT, especially the serotonin trans-porter (SERT). The effect of this lack of selectivity for in vivo imaging is unknown. In this study, we compared the SPECT radioligands 123I-2-b-carbomethoxy-3b-(4-iodophenyl)-N-(3-fluoropropyl)nortropane (123I-FP-CIT) and 123I-N-(3-iodoprop-2E-enyl)-2-b-carbomethoxy-3b-(4-methylphenyl) (123I-PE2I). 123I-FP-CIT has a 10-fold higher selectivity than 123I-FP-CIT for DAT versus SERT. Methods: Sixteen healthy individuals were scanned in random order with both radioligands. The radioligands were administered according to standard recom-mendations: 123I-FP-CIT was given as a bolus injection, and the ratio between the striatum and reference tissue was measured after 3 h. 123I-PE2I was administered in a bolus–infusion setup