Quantitative Analysis of NK1 Receptor in the Human Brain Using PET with 18F-FE-SPA-RQ

18F-fluoroethyl-SPA-RQ (18F-FE-SPA-RQ) was recently devel-oped as a radioligand for themeasurement of neurokinin 1 (NK1) re-ceptorwith PET. In this study, we used 18F-FE-SPA-RQwith PET to visualize and quantify NK1 receptor in the human brain.Methods: PETscanswereperformedon7healthymenafter intravenous injec-tion of 18F-FE-SPA-RQ. Binding potential (BPND) was calculated by theindirectkinetic,simplifiedreferencetissuemodel (SRTM),andra-tiomethods. The indirect kineticmethodwasusedas the gold stan-dardmethod andwas comparedwith the SRTMmethod,with scan times of 180, 270, and 330min, andwith the ratiomethod,with time integration intervals of 120–180, 210–270, and 300–330 min. The cerebellum was used as the reference brain region. Results: Re-gional radioactivity was highest in the caudate head and putamen; mid level in the parahippocampus, cerebral cortex, and thalamus; and lowest in the cerebellum. BPND values by the indirect kinetic method were 3.15 6 0.36, 3.11 6 0.66, 1.17 6 0.25, and 0.46 6 0.14 in the caudate, putamen, parahippocampal region, and thala-mus, respectively. For cerebral cortical regions, BPND values by the indirect kineticmethodwere 0.946 0.23, 0.826 0.15, 0.766 0.15, and 0.696 0.16 in the occipital, temporal, frontal, and anterior cin-gulate cortices, respectively. BPND values by the SRTM and ratio methods were in good agreement with those by the indirect kinetic method (r 5 0.94–0.98). Conclusion: The regional distribution of 18F-FE-SPA-RQ was in agreement with previous PET studies and postmortem studies of NK1 receptor in the human brain. The ratio method will be useful for clinical research of psychiatric disorders, for the estimation of NK1 receptor without arterial blood sampling and long dynamic PET