PET imaging in chemical biology

Institucio Catalana de la Reserca i Estudis Avangats (ICREA) and Institute of Chemical Research of Catalonia (ICIQ), 43007 Tarragona, Spain 

This chapter will concentrate on PET as a molecular imaging modality. An introduction to the technique will first be provided followed by specific examples where PET has been successfully used to obtain a better understanding of specific biological processes, in the detection of disease and also as a tool for drug discovery and development. 

Chemical Biology Edited by Banafshe Larijani, Colin. A. Rosser and Rudiger Woscholski 2006 John Wiley Sons, Ltd 

The existence of positron was first proposed by P.A.M. Dirac in the late 1920s and was experimentally discovered in 1932. A positron is the antimatter counterpart of an electron and hence has the same mass as the electron but opposite charge. The process by which a nucleus undergoes positron decay generates a new nucleotide with one fewer proton and one more neutron, besides emitting one positron and a neutrino. 

Similarly to what occurs to an electron, when a positron passes through matter it experiences a loss of energy through ionization and excitation of nearby molecules and atoms. At some point (typically after having travelled a distance of approximately 1 mm) the positron has lost enough energy to be annihilated by colliding with an electron close by. 

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