Fluorine-18 Labeled Amino Acids for Oncologic Imaging with Positron Emission Tomography

18F-labeled amino acids are an important class of imaging agents for positron emission tomography (PET) that target the increased rates of amino acid transport by many tumor cells. This class of tracers is structurally diverse, and the biological and imaging properties of a given 18F-labeled amino acid depends largely upon its mechanism of transport. The system L amino acid transport system has been a major focus of tracer development in this field, but more recently 18Flabeled amino acids have been developed for other transporters including system A, glutamine, glutamate and cationic amino acid transport systems. Radiolabeled amino acids are best established for brain tumor imaging, but there are emerging applications in other types of cancer such as neuroendocrine tumors and prostate cancer. This review provides an overview of 18F-labeled amino acids for oncologic imaging in terms of design considerations, radiosynthetic methods, and key clinical applications.