Novel single-photon-emitting radiopharmaceuticals for diagnostic applications

The armamentarium of approved radiopharmaceuticals for either diagnosis or therapy is at the core of the clinical practice of today's nuclear medicine. Nevertheless, both because the currently approved agents do not meet all the clinical needs for radionuclide targeting and because advancing knowledge in the pathophysiology of tissues/organs opens in turn new opportunities, investigations continue at the preclinical and clinical validation level for the development of new radiopharmaceuticals, most of which are not approved yet for commercial use. Concerning in particular the diagnostic applications of nuclear medicine to oncology, ongoing investigations in the search for tumor-targeting agents with better specificity and sensitivity are countless, possibly within the scenario of theranostics-that is, with the dual potential for imaging and for therapy, depending on the specific radionuclide employed for radiolabeling. We will focus this chapter on the most promising imaging agents labeled with single-photon-emitting radionuclides based on some of the mechanisms that are typical for tumor cells/tissues.