Despite advancement in pain management, pain relief and patient satisfaction are still inadequate in many patients. Functional imaging techniques have recently made it possible to identify the main cerebral components of the human nociceptive system. These comprise at least two main human nociceptive components working in parallel called the medial and lateral pain systems. This has provided a physical construct for the concept of the human pain matrix. Careful study of these areas of the human brain has the potential to drive development of new classes of analgesic compounds. PET is an imaging technique that can quantify increases in nerve cell activity in selective regions of the brain (1-5). PET provides the means to measure tissue concentrations of labeled drugs in brain and other tissues and also to measure changes in receptor occupancy.