Positron Emission Tomography (PET) Use in Pharmacology

Abstract

Positron emission tomography (PET) is a sensitive and specific noninvasive imaging technology used to measure the 3-dimensional distribution of molecules and their functional outcome over time. This is achieved by detecting the annihilation photons resulting from the decay of radioisotopes (i.e., oxygen-15, nitrogen-13, carbon-11, fluorine-18) chemically labeled to biologically active molecules. The functional fate of these radiolabeled molecules may be determined by examining the images formed from the 3-dimensional reconstruction of the decay events. The approximate sensitivity of PET is picomolar, which permits the injection of molecular masses far below that known to disturb most physiological processes. This methodology is known as the “tracer technique” and is the basic analysis principle used to extract quantitative information from PET images. PET has the ability to provide valuable information related to functional processes of the body including blood flow, transport rates, receptor density, and drug occupancy. This chapter focuses on the physics of PET and its use in answering questions related to pharmacology. The basic principles of PET imaging will be reviewed followed by methods to derive quantitative information related to physiology from the image data. The application of compartmental modeling will be discussed in detail as will potential pitfalls that can occur during data collection.