MRI contrast agents
Metal complexes, and particulary Gadolinium complexes, of tetraazacycloalkanes are used as contrast agents for magnetic resonance imaging (MRI).
PET and SPECT contrast agents
Macrocyclic complexes of radiometals are used as contrast agent for Positron Emission Tomography and Single-Photon Emission Computed Tomography. Generally, theses applications require the synthesis of bifunctional chelating agents in order to connect the radiometal complexe to a biomolecule such as monoclonal antibodies or peptides.