Techniques for the Incorporation of Fluorine-18 and Carbon-11

Abstract

Molecular imaging is an attractive modality that has been widely employed in many aspects of biomedical re-search, especially those aimed at the early detection of diseases such as cancers, inflammation and neurodegenerative disor-ders. One specific type of molecular imaging, which has shown a renewed interest in recent years, comes in the form of positron emission tomography (PET). This type of imaging relies on the formation of small molecule drugs that have been selectively labeled with a positron emitting radionuclide. Ide-ally, the small molecule will have a high affinity for the mo-lecular target, cell line or physiological process to be imaged, which allows for the accumulation of the agent. The predict-able mode and rate of decay associated with the chosen nuclide allows for both spatial and quantitative imaging of the tissues associated with the small molecule radiotracer when con-trasted against the surrounding tissue that lacks the character-istic radioactive decay. Over the many years of radiotracer development, various methods for the incorporation of the radionuclide have been discovered and utilized. Much of this experimentation has shed light on the types of reaction sub-strates, solvents, temperatures and reactant forms that allow for the most efficient and repeatable labeling of a given class of molecule. This paper will highlight many of the previously attempted, currently used and potential reactions for the in-corporation of either fluorine-18 or carbon-11 radionuclides onto both small molecule and macromolecular drugs. This will include both aliphatic and aromatic labeling techniques and the types of products and potential by-products one may ob-serve.