In111

Indium-111 (111In) is a radioactive isotope of the element indium used in diagnostic nuclear medicine. It decays by electron capture to stable cadmium-111 with a half-life of about 2.8 days, emitting gamma rays at energies of approximately 171 keV and 245 keV that are suitable for single-photon emission computed tomography (SPECT).

Production and chemical forms of indium-111 vary by facility. It is typically produced in nuclear reactors or cyclotrons by irradiation of targets such as cadmium or tin and then chemically separated to yield usable forms, commonly indium-111 chloride or chelated complexes. These forms enable labeling of a range of biologically active carriers, including antibodies, peptides, and cells.

Medical applications of Indium-111 radiopharmaceuticals are diverse. In-111 pentetreotide (octreotide chelate) is used for imaging neuroendocrine tumors. In-111 labeled leukocytes (often via In-111 oxine) are employed for infection and inflammation imaging. In-111 labeled antibodies such as capromab pendetide (ProstaScint) have been used for prostate cancer imaging. Additional agents include various In-111 chelates and conjugates used in research and clinical imaging to study organ function or disease processes.

Safety and regulation: Indium-111 radiopharmaceuticals require specialized handling, radiation safety measures, and clinical oversight. Administered activities are chosen to balance image quality with patient radiation dose and depend on the specific radiopharmaceutical. Providers follow regulatory guidelines for production, labeling, and disposal to minimize exposure.