A technetium generator consists of molybdenum-99 exposed to neutron radiation to make some of the nuclei unstable. Some of the nuclei decay to metastable technetium, and if sodium chloride passed through a column consisting of Mo-99, ion-exchange occurs between chloride ions and pertechnate ions. A solution containng pertechnate ions is obtained. This can be injected into the blood a subject and used in diagnoses e.g. in brain scans, using a gamma camera. For imaging bones, a phosphate tracer labelled with Tc-99 can be used.