This is a specialised scanning method using very small amount of low-level radioactive isotopes injected into the bloodstream. Once administered these radioactive tracers can localise to specific organs where the scanner, called a gamma camera, is used to measure the radiation levels given off from the isotopes. This allows assessment of the functional abnormalities in very specific parts of the body such as: assessment of thyroid function, location of tumours and possible spread, checking of bone fractures and assessing damage to the heart after coronary episodes.