PT - JOURNAL ARTICLE AU - Mika Naganawa AU - Ming-Qiang Zheng AU - Shannan Henry AU - Nabeel Nabulsi AU - Shu-Fei Lin AU - Jim Ropchan AU - David Labaree AU - Soheila Najafzadeh AU - Michael Kapinos AU - Johannes Tauscher AU - Alexander Neumeister AU - Richard E. Carson AU - Yiyun Huang TI - Test–Retest Reproducibility of Binding Parameters in Humans with <sup>11</sup>C-LY2795050, an Antagonist PET Radiotracer for the κ Opioid Receptor AID - 10.2967/jnumed.114.147975 DP - 2015 Feb 01 TA - Journal of Nuclear Medicine PG - 243--248 VI - 56 IP - 2 4099 - http://jnm.snmjournals.org/content/56/2/243.short 4100 - http://jnm.snmjournals.org/content/56/2/243.full SO - J Nucl Med2015 Feb 01; 56 AB - 11C-LY2795050 is a new antagonist PET radioligand for the κ opioid receptor (KOR). In this study, we assessed the reproducibility of the binding parameters of 11C-LY2795050 in healthy human subjects. Methods: Sixteen healthy subjects (11 men and 5 women) underwent 2 separate 90-min PET scans with arterial input function and plasma free fraction (fP) measurements. The 2-tissue-compartment model and multilinear analysis-1 were applied to calculate 5 outcome measures in 14 brain regions: distribution volume (VT), VT normalized by fP (VT/fP), and 3 binding potentials (nondisplaceable binding potential, binding potential relative to total plasma concentration, and binding potential relative to free plasma concentration: BPND, BPP, BPF, respectively). Since KOR is distributed ubiquitously throughout the brain, there are no suitable reference regions. We used a fixed fraction of individual cerebellar VT value (VT,CER) as the nondisplaceable VT (VND) (VND = VT,CER/1.17). The relative and absolute test–retest variability and intraclass correlation coefficient were evaluated for the outcome measures of 11C-LY2795050. Results: The test–retest variability of 11C-LY2795050 for VT was no more than 10% in any region and was 12% in the amygdala. For binding potential (BPND and BPP), the test–retest variability was good in regions of moderate and high KOR density (BPND &gt; 0.4) and poor in regions of low density. Correction by fP (VT/fP or BPF) did not improve the test–retest performance. Conclusion: Our results suggest that quantification of 11C-LY2795050 imaging is reproducible and reliable in regions with moderate and high KOR density. Therefore, we conclude that this first antagonist radiotracer is highly useful for PET studies of KOR.