Modeling analysis of the new kappa opioid receptor antagonist tracer [11C]LY2795050 in humans

Methods: Seven healthy volunteers (age=26±6) underwent 120-min scans with [C]LY2795050 on the HRRT scanner. The subjects received a bolus injection of 482±171 MBq, the specific activitywas 23±8 MBq/nmol, and the injectedmasswas 8.8±1.2 μg. Imageswere reconstructedwith a list-mode reconstruction algorithm which incorporates event-by-event motion correction. Regional TACs were created by registering an early summed image to eachsubject'sMRwhichwas then registered to theAAL template. TheseTACswere fitted to the2Tmodelwithmetabolite-corrected plasma input function to estimate VT. BPND values were computed as [VT(ROI)/VT(CER)]−1, with cerebellum as the reference region. ROI TACs were also fitted using SRTM and BPND results were compared with those derived from the 2T model. In addition, BPND values were computed employing only the first 90 min of scan data, and these estimates were compared to the 120-min values. Finally, parametric images of BPND were created with SRTM2, matching ROIs were applied to these images, and the resulting BPND values were compared to those obtained by regional TAC fitting.