text: Many other isotopes have been used in specialized radiopharmacological studies. The most widely used is Ga for gallium scans. Ga is used because, like Tc, it is a gamma-ray emitter and various ligands can be attached to the Ga ion, forming a coordination complex which may have selective affinity for particular sites in the human body.
  An extensive list of radioactive tracers used in hydraulic fracturing can be found below.