Pharmacokinetic Challenges against Brain Diseases with PET

Positron emission tomography (PET) is an imaging technology used to visualize distribution of particular ligands inside living organisms. The ligand is labeled by a positron-emitting isotope, such as 11C, 15O, 13N and 18F, and injected into subjects. By detecting γ-rays emitted from the ligand, in vivo biodistribution and kinetics of the ligand can be depicted with high sensitivity. By altering the target ligand for PET, one can see different distributions and time courses of the target. PET provides several biological and functional images inside the body, rather than simply an anatomical image. Therefore, PET can potentially detect biological changes that occur long before anatomical changes begin. PET has been widely used for neuroreceptor and neurotransmitter studies by tracing radioligands, which have selective affinity for a particular site. For example, the dopamine and serotonin receptors are highly related to brain disorders. By analyzing the pharmacokinetics of these ligands using PET, it is possible to noninvasively detect abnormalities in the brain. However, signals from PET contain many different types of information, and it is important to interpret the signals appropriately and choose the proper technique to analyze PET data. This chapter discusses several analytical methods for PET data.