In the scan above, a compound has been tagged with molecules of a radioactive substance with a short half life. This is then injected into the blood stream and its progress through the urinary system observed with a gamma camera, which detects the gamma rays given off as the radioactive source decays. In this way any abnormalities such as blockages and tumours can be observed. The short half life means that the radioactive material will decay to a stable isotope quickly where it will no longer be capable of doing any damage to the body and will leave the body in the normal way.
Radioactive Isotopes are often used to create images of internal organs