ABSTRACT
Positron emission tomography (PET) is a nuclear medicine imaging technique that provides a powerful and sensitive means to noninvasively investigate biological processes in vivo. After the administration of a suitably radiolabeled pharmaceutical into the subject, images of the static or dynamic distribution of the tracer can be formed that provide information on blood flow, metabolism, cellular proliferation, angiogenesis, hypoxia, receptor and enzyme concentrations, gene expression, etc. The idea to detect the back-to-back 511-keV radiation in coincidence for measuring internal structures of the body was first proposed independently in 1951 by Sweet and Wrenn et al. PET is based on the coincidence detection of the two collinear 511-keV photons resulting from the annihilation of an electron, with the positron emitted during ß+ decay. The effect of the positron range on resolution is radionuclide-specific and depends on the ß+ emission energy. Its distribution profile in tissue-equivalent materials has a sharply peaked shape that can be modeled as the sum of two exponentials.
