The Nuclear Medicine Test for Thyroid

In the field of nuclear medicine, specialists use isotopes to diagnose and treat various conditions. A thyroid scan is a nuclear medicine test that employs an unstable isotope of iodine to diagnose conditions of the thyroid gland.

The Thyroid Gland

• The thyroid affects virtually every system of the body.

  The thyroid is a gland in the neck that plays an important role in metabolism. An abnormally functioning thyroid can be either overactive, which is called hyperthyroid, or underactive, which is called hypothyroid.

Unstable Isotopes

• The throid is located in the neck.

  A chemical element can exist in different forms, called isotopes, depending on the number of neutrons in the nucleus of its atoms. Certain isotopes of many elements are unstable, which is to say radioactive. Over time, the nuclei of their atoms release energy until they become stable.

Radioactive Iodine

• The thyroid gland is vital to metabolic function.

  Iodine is vital to the function of thyroid cells. Thus, an isotope of iodine known as iodine-123, or I-123, is useful in diagnosing thyroid conditions. When cells are more active, they take up more iodine from the blood.

Monitoring

• An unstable isotope is an isotope that is radioactive.

  Because I-123 is unstable, it releases energy constantly. In a thyroid scan, I-123 is injected into the blood. Radiation detectors (special cameras) are then pointed at the neck, and the thyroid gland can be imaged. Based on how quickly I-123 is absorbed into the thyroid, and the patterns in which different parts of the gland absorb it, thyroid disorders can be diagnosed.

Thyroid Conditions

• Radioactive Iodine can be used to diagnose many conditions.

  Conditions that can be diagnosed using I-123 scanning include hyperthyroidism and hypothyroidism (each of which has many possible causes) and various thyroid tumors.