TY - JOUR T1 - Test-retest variability of 5-HT6 binding in striatum using the PET tracer [11C]GSK215083 in humans JF - Journal of Nuclear Medicine JO - J Nucl Med SP - 1196 LP - 1196 VL - 52 IS - supplement 1 AU - Beata Planeta-Wilson AU - Nabeel Nabulsi AU - Shu-fei Lin AU - Soheila Najafzadeh AU - Irina Esterlis AU - Elyse Katz AU - Timothy McCarthy AU - Richard Carson AU - Evan Morris AU - Yiyun Huang Y1 - 2011/05/01 UR - http://jnm.snmjournals.org/content/52/supplement_1/1196.abstract N2 - 1196 Objectives [11C]GSK215083 is a novel PET radiotracer binding to both 5-HT6 and 5-HT2A receptors, with predominantly 5-HT6 binding in the striatum (1). The goal of the present study was to examine the test-retest variability of [11C]GSK215083 for use in assaying 5-HT6 receptors in the striatum in humans. Methods Six healthy male volunteers (mean age 33±9yo) participated in a test-retest protocol, two scans per day. The injected dose was 587±152MBq, specific activity at time of injection was 106 ± 68 MBq/nmol and the injected mass was 0.045 ± 0.032 µg/kg. A 120-min dynamic acquisition on the HR+ camera was performed; time-activity curves were generated for caudate, putamen, and cerebellum (used as a reference region). The TACs were fitted with SRTM and MRTM) models. Additionally, 1- and 2-tissue (1T, 2T), and multilinear (MA1) models with a metabolite corrected arterial input function were applied. For 1T, 2T and MA1, the non-displaceable binding potential (BPND) was calculated from volume of distribution (VT) values with cerebellum as the reference. Test/retest variability in BPND values across subjects were calculated as |(test-retest)|/avg[test, retest] by region. Results Data were best fitted with SRTM and MRTM (equilibrium cutoff, t*=40) models, test/retest values were: SRTM: 47.9±21.0% for caudate and 35.1±14.7 for putamen; MRTM 34.3±15.7% for caudate and 75.7±69.2% for putamen; MA1 19.8±10.6% for caudate and 16.6±12.7% for putamen. The 2T model produced unreliable VT values. In addition, 90 min of data produced VT that correlate (r2 = 0.85) with 120 min of data with only slight underestimation when using the MA1 model. Conclusions The MA1 model produced the best test-retest reproducibility of BPND values for striatal regions. Reliable estimates of BPND in the striatum may be possible from 90 min of scan data. 1. Parker et al. Neuroimage 2008, 41:T20 Research Support Pfize ER -