 Iodine-123

Iodine-123 (123I) is a radioactive isotope of iodine used in nuclear medicine imaging, including single photon emission computed tomography (SPECT) or SPECT/CT exams.The isotope's half-life is 13.22 hours; the decay by electron capture to tellurium-123 emits gamma radiation with a predominant energy of 159 keV (this is the gamma primarily used for imaging).