What are we measuring with PET?

Positron emission tomography is a medical imaging technique that provides u nique information concerning many biochemical mechanisms underlying normal physiologic function. With respect to the central nervous system (CNS), sel ective radiolabeled compounds targeted at specific neurotransmitter recepto r systems reveal information not only concerning receptor distribution and enzymatic activity but neurotransmitter concentrations as well. Recent adva nces in our understanding of these systems may be utilized to further under stand changes in brain biochemistry that either result from or produce symp tomatology associated with many CNS disease states. The ability to measure interactions between neurotransmitter systems in the human brain may also a dd to our knowledge of drug side effects and disease progression. While man y CNS diseases have been defined as "neurotransmitter-specific" in nature, scientific data now suggests that changes in multiple neurotransmitter syst ems are evident in the brains of patients suffering from these classically described diseases. PET is a powerful tool that can be used to examine many of these changes in the living human brain.