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The serotonin transporter tracer [C-11]AFM provides high specific binding signals in humans

¹ Diagnostic Radiology; ² Psychiatry, Yale School of Medicine, New Haven, Connecticut

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Objectives: The serotonin transporter (SERT) ligand [C-11]AFM in baboons has produced better specific binding signals than [C-11]DASB (Huang: JCBFM 2002). We conducted first-in-human study to assess the imaging qualities of this new tracer.

Methods: Radiosynthesis was performed with [C-11]methyl triflate on the FxC automated module. PET imaging was conducted on the HRRT scanner. Five healthy subjects were studied, each with two scans of 120 min duration: a test scan followed by a re-test scan on the same day. Imaging data were analyzed using the Simplified Reference Tissue Model (SRTM2) and binding potentials (BP) calculated.

Results: [C-11]AFM was prepared in 95% radiochemical and chemical purities. Specific activity was 11 ± 4 Ci/µmol (EOS) and injected dose was 19 ± 1 mCi. [C-11]AFM displayed high uptake in the brain. In all regions equilibrium was reached between 40 and 80 min post-injection. Test retest reproducibility was good, with 5% average difference in regional BP between the two scans. Mean BPs for all subjects were 3.3, 2.3, 2.2, 1.9, 0.9 in the raphe, thalamus (THA), amygdala (AMG), striatum (STR), and hippocampus (HIP), respectively. These values compare favorably with [C-11]DASB, which provides BPs of 1.1 (AMG & THA), 1.0 (STR), and 0.4 (HIP) (Frankel: JNM 2006 and Biol Psychiat 2005). Furthermore, [C-11]AFM BPs in the cortical areas were 3 to 5 times higher than those afforded by [C-11]DASB: 0.83, 0.51, 0.50, and 0.48 vs 0.29, 0.17, 0.11 and 0.10 in the cingulate, temporal, frontal and occipital cortices.

Conclusions: [C-11]AFM provides high specific binding signals in the human brain and is an excellent PET tracer to image the SERT, especially in low density areas such as the cortex.

Research Support: NIMH (MH066624)

This Article Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Nabulsi, N. Articles by Huang, Y. PubMed Articles by Nabulsi, N. Articles by Huang, Y.