A radiopharmaceutical is a (radio)labelled molecule, and as a conventional pharmaceutical, is a drug designed and formulated for targeting within the human body, specific organs, tissues or cells, often via selected biological functions or metabolic pathways and via pharmacological binding / interfering sites (e.g. receptor, enzyme). A radiopharmaceutical is thus predominantly a chemical combination / association of (stable) biogenic atoms (C, H, O, N) – a structure also often called vehicule or vector, since the latter part of the molecule is largely responsible for the targeting or binding properties of the radiopharmaceutical – comprising (when isotopic labelling is concerned) or associated to (in case of non-isotopic labelling, e.g. radiohalogens, radiometals) a radioactive isotope. The radioisotope may be a gamma- or X-Ray emitter, and as such the radiopharmaceutical will be used as a diagnostic tool in nuclear medicine (via single photon emission computed tomography (SPECT) imaging); it may also be a positron-emitter (leading to the emission of two 511 keV gamma rays in coincidence) and associated to (diagnostic) positron emission tomography (PET) imaging. The radioisotope may alternatively be an alpha-emitter or a beta (minus) / auger-electron-emitter, permitting to the radiopharmaceutical to serve as an in vivo, non-invasive, therapeutic agent (vectorized internal radiotherapy). Combination of radioactive pairs of emitters may also provide theranostic radiopharmaceuticals (combining both therapeutic and diagnostic imaging applications), which in combination with sophisticated high-performance digital hybrid imagers (SPECT/CT, PET/CT, and PET/MRI), have started to play a major role in precision medicine by significantly improving patient disease management, particularly in oncology.

The given presentation will give an overview of the radioisotopes used in nuclear medicine, both for diagnostic and therapeutic applications, define the challenges associated to their incorporation into a molecule as well as provide selected examples of synthesis of radiopharmaceuticals labelled with these radioisotopes.