TY - JOUR T1 - Test–Retest Reproducibility of Binding Parameters in Humans with <sup>11</sup>C-LY2795050, an Antagonist PET Radiotracer for the κ Opioid Receptor JF - Journal of Nuclear Medicine JO - J Nucl Med SP - 243 LP - 248 DO - 10.2967/jnumed.114.147975 VL - 56 IS - 2 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 Y1 - 2015/02/01 UR - http://jnm.snmjournals.org/content/56/2/243.abstract N2 - 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. ER -