Radioactive Tracers

In some cases, injected radioactive sources (such as technetium-99) can be used as tracers to make soft tissues, such as blood vessels or the kidneys, show up through medical imaging processes.

An isotope emits gamma rays that easily pass through the body to a detector outside the body, for example a ‘gamma camera’.

In this way, the radioactive isotope can be followed as it flows through a particular organ in the body.

Changes in the amount of gamma emitted from different parts would indicate how well the isotope is flowing, or if there is a blockage.

The isotope used must:

  • be a source of gamma rays so that they pass out through the body to be detected by the gamma camera or GM tube;
  • have very short half-lives - sources used typically have half-lives of hours so after a couple of days there will hardly be any radioactive material left in a person’s body;
  • not be poisonous.