Nuclear medicine specialists are doctors who have extensive training in the use of nuclear substances, like radiation, to diagnose and treat certain illnesses.These specialists perform diagnostic tests in which a small amount of a radioactive substance is injected into a vein, inhaled or taken orally by the patient. The radioactive substance then enables the nuclear medicine specialist to use a scanner to detect the radiation level in the part of the body being examined in order to create an image of it with a computer. The images tell the physician whether there are abnormal changes in metabolism which indicate whether a disease or injury is present. These tests are often used to detect cancer.In addition to detecting cancer, substances like radioactive iodine can be either injected into the blood stream or taken orally to fight cancer and other diseases. After being ingested, the substance is absorbed by the thyroid gland and abnormal thyroid tissues are destroyed.