<qa>  What is the primary goal of this study?This study has two primary objectives. First, we will determine whether the uptake of 11CPS13 in brain and periphery reflects the distribution of COX-1, as demonstrated by blocking with a COX-1 preferential drug aspirin and no effect with a COX-2 selective drug celecoxib. Second, we will measure the testretest reproducibility of brain uptake quantified by compartmental modeling and using arterial blood samples. 