Quantitative Analysis of NK 1 Receptor in the Human Brain Using PET with 18 F-FE-SPA-RQ

18F-fluoroethyl-SPA-RQ (18F-FE-SPA-RQ) was recently developed asa radioligand for the measurement of neurokinin1 (NK1)receptor with PET. In this study, we used 18F-FE-SPA-RQ withPET to visualize and quantify NK1 receptor in the human brain. Methods: PETscanswereperformedon7healthymenafterintravenousinjection of 18 F-FE-SPA-RQ. Binding potential (BPND) was calculated by theindirectkinetic,simplifiedreferencetissuemodel(SRTM),andratiomethods.Theindirectkineticmethodwasusedasthegoldstandard method and was comparedwith the SRTMmethod, withscan timesof180, 270,and330min, and withthe ratiomethod, withtime integration intervals of 120‐180, 210‐270, and 300‐330 min. The cerebellum was used as the reference brain region. Results: Regional 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 thalamus, respectively. For cerebral cortical regions, BPND values by the indirect kinetic method were 0.94 6 0.23, 0.82 6 0.15, 0.76 6 0.15, and 0.69 6 0.16 in the occipital, temporal, frontal, and anterior cingulate 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 18 F-FE-SPA-RQ was in agreement w ith 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.