Diagnostic nuclear medicine involves using small amounts of radioactive substances to assess the function of bones, tissues and organs. The results are used to help diagnose the cause of a disease. Radioactive materials used in this type of medical testing are relatively safe because they are used in amounts which give off no more radiation than a standard diagnostic X-ray. In most diagnostic nuclear medicine procedures, radioactive substances are swallowed, inhaled or introduced into a vein. Medical imaging scans are then carried out which can be used to assess function by showing how much radioactive material has collected in an organ or tissue.
Radionuclides are substances which undergo what is called radioactive decay. During this process, a type of radiation known as gamma rays is given off. In the field of diagnostic nuclear medicine, radionuclides are combined with drugs to form what are called radiopharmaceuticals, which may then be administered to patients. The benefits of nuclear medicine tests include the fact that they give information about tissue function as well as appearance. They are painless and accurate, can scan a wide area and are less invasive than a surgical investigation.
Positron emission tomography (PET) is a procedure commonly used in diagnostic nuclear medicine. A PET camera is used to detect gamma rays in the part of the body being investigated. The information is then fed to a computer and an image of the body tissue is displayed, showing the radioactive areas. PET is useful because it can reveal changes during the initial stages of an illness, enabling earlier diagnosis and disease treatment. Information about a variety of problems, such as cancers, brain disorders and heart disease, may be obtained from PET scans.
Some diagnostic nuclear medicine procedures do not involve the use of images. In these types of tests, blood samples are taken following the injection of radiopharmaceuticals. Patients are typically awake during nuclear medicine investigations but different tests take varying amounts of time to perform. This is because radioactive materials may travel through the body at different rates, and accumulation in the target tissue could occur hours or days after a substance has been administered.
Techniques which are similar to those used in diagnostic nuclear medicine, and which involve administering radioactive substances to a patient, are sometimes used as a medical treatment. For example, radioactive iodine may be swallowed and used to treat an overactive thyroid gland. The radioactive material collects inside thyroid cells and destroys them.
