 For whole body imaging, organ uptake will be quantified as a Standardized Uptake Value SUV, which normalizes for injected activity and body weight. Blockade by aspirin and celecoxib will be expressed as a percentage of the baseline scan in each subject and plotted relative to the plasma concentration of the drug at time of the PET scan. For dedicated brain imaging, uptake will be quantified as distribution volume VT calculated with compartmental modeling and serial concentrations of parent radioligand in arterial plasma. 