Radioactive Iodine Thyroid Diagnostic Scan and Uptake

Radionuclide Diagnostic Imaging

Iodine 123I and technetium 99mTc pertechnitate are the substances used to determine the functional activity and partially the structure of the thyroid. The testing for the radioactive iodine uptake and scan is a two-day test that requires the use of imaging machinery such as a gamma camera or preferably a rectilinear scanner that moves over the area of interest. It is a very simple test that is based on the concept that the thyroid is the primary organ in the body that metabolizes and uses iodine. A patient swallows an extremely small amount of 123I or 99mTc as a capsule or liquid and then images of the thyroid or body are taken four hours later and 24 hours later. See more details in our radioactive iodine clinic section.

The radioactive iodine scan is the best test to evaluate the possible causes of thyrotoxicosis, the presence of excess thyroid hormone in the body. The test is most useful in the setting of a patient that has been evaluated by an endocrinologist to be clinically hyperthyroid, and preferably with biochemical testing supporting the diagnosis of hyperthyroidism. The specialists at Houston Thyroid and Endocrine can help patients to properly order and interpret these types of scans.