Radioactive iodine thyroid imaging with

Nuclear Medicine iodine-131 is a radioactive isotope that is absorbed by the thyroid gland. It is used in medicine to diagnose and treat diseases of the thyroid. When iodine-131 is administered to a patient, radiation from the isotope creates an image of the gland on film that reveals abnormalities. The image above shows the thyroid of a patient with Graves disease, a treatable disease that is a common cause of an overactive thyroid gland. 

With the production of artificial radioactive substances in 1934. the field of nuclear medicine was established. In 1937, the first radioactive isotope was used to treat a person with leukemia at the University of California at Berkeley. Major strides in the use of radioactivity in medicine occurred in 1946, when a radioactive iodine isotope was successfully used to diagnose thyroid function and to treat hyperthyroidism and thyroid cancer. Radioactive substances are now used to produce images of organs, such as liver, spleen, thyroid gland, kidneys, and the brain, and to detect heart disease. Today, procedures in nuclear medicine provide information about the function and structure of every organ in the body, which allows the nuclear physician to diagnose and treat diseases early. 

The use of radioactivity in diagnosis usually involves a radiotracer, a radioactive nuclide attached to a compound or introduced into a mixture in order to track the movanent of the compound or mixture within the body. Tracers are useful in the diagnosis of disease because of two main factors (1) the sensitivity with which radioactivity can be detected, and (2) the identical chemical behavior of a radioactive nucleus and its nonradioactive counterpart. For example, the thyroid gland naturally concentrates iodine. When a patient is given small amounts of iodine-131 (a radioactive isotope of iodine), the radioactive iodine accumulates in the thyroid, just as nonradioactive iodine does. However, the radioactive iodine emits radiation, which can then be detected with great sensitivity and used to measure the rate of iodine uptake by the thyroid, and thus to image the gland. 

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