A wide range of compounds are used in PET. These positron-emitting radionuclides have short half-lives and high radiation energies compared with radioisotopes generally used in biomedical research. [2] The main positron- emitting radionuclides used in PET include Carbon-11, Nitrogen-13, Oxygen-15, and Fluorine-18, with half-lives of 20 min, 10 min, 2 min, and 110 min respectively. These compounds are commonly known in PET as tracer compounds and throughout time have become increasingly important as scientists have learned to work with their short half-lives.
Due to the fact that these elements are found in almost if not all of the
compounds that are consumed by the human body it only makes sense that PET is an
obvious technique to study the fate of these compounds in vivo. [3] These tracer
compounds are administered by means of injection or inhalation, the purpose
being simply to enter the compound into the bloodstream. [14] It is the short
half-lives of these tracers that allow large doses to be administered to the
patient with low radiation exposure and enable studies to be repeatedly
performed. In the past, these short half-lives presented grave problems, and at
times still do. In order for a facility to produce these radionuclides it is
necessary for the center to be equipped with a particle accelerator (cyclotron),
a team of nuclear physicists, computer experts, radiopharmacists, isotope
specialists, and clinicians. [14] Unless a facility has the means of carrying
out this synthetic process the radionuclides must be transported to the site
where they will be used. Of the four radionuclides Fluorine-18 is the ideal
candidate for transport. Over the past several years, PET has been undergoing
very rapid development, mainly due to the multitude of new tracer substances
available for human studies. [4]
Last modified: December 5, 1995