Nuclear Medicine

Nonimaging nuclear medicine exams such as radioimmunoassay studies require mixing serum with radioactive tracers to detect the presence of a certain hormone, chemical, or therapeutic drug. In other nonimaging studies the patient is given a radiopharmaceutical, and after a certain amount of time, samples of blood or urine are obtained and tested. Occasionally, a large amount of a radioactive substance is given to a patient to produce a biologic effect. For example, the therapeutic treatment for Grave's disease, a hyperactive condition of the thyroid gland, requires a high dose of radioactive iodine (¹³¹I)—enough to destroy thyroid tissue. Radioactive iodine is often used to treat or detect thyroid conditions because the thyroid naturally organifies, or "traps," iodine a person's thyroid cannot tell the difference between stable or radioactive iodine. When radioactive iodine is ingested, the thyroid, depending on its physiological state, absorbs a certain amount, temporarily making the thyroid radioactive.