Thyroid Uptake and Scan

The thyroid uptake and scan is a radiologic diagnostic tool to determine thyroid function and pathologies. This diagnostic procedure works on the principle of the unstable nuclide of the atom, which tries to attain stability by releasing an alpha, beta, and gamma rays. Clinicians use these rays for diagnostic and treatment purposes.The test uses a radioactive tracer, which is a protein or a molecule attached to radioactive material. The radioactive tracer is administered into the patient, and a probe measures the amount of iodine uptake by the thyroid gland. The thyroid scan checks for the even spread of the tracer in the gland. More than 20 radioactive tracers exist, of which two isotopes of iodine I-123 and I-131 and 99m-technetium pertechnetate, are the usual agents used in this test. I-131 has a longer half-life than I-123, so I-123 is used more frequently than I-131 due to less radiation exposure to the body. 99m-Technetium pertechnetate is an analog of iodine, so it gets transported to the thyroid gland similarly to iodine. 111In-pentoxide, thallium-201 (201T1), 99mTc-sestamibi, 99mTc-tetrofosmin are some of the less commonly used radioactive tracers in this test. This test is different than radioactive iodine therapy, which treats thyroid cancers.