Overview

The thyroid gland can be studied a number of ways in the Nuclear Medicine department. Because the thyroid normally needs iodine to make thyroid hormone, a radioactive isotope of iodine is used which allows us to measure how well the thyroid gland is functioning (thyroid iodine uptake) and to obtain images of the thyroid gland (thyroid scan).  Both the uptake and scan procedures usually involve two visits to the Nuclear Medicine Department.

On the first day, you will be asked to swallow a small amount of radioactive iodine in a capsule. This visit should take about fifteen minutes.  The next day, you will return for the scan and uptake procedures, which will take one hour or longer.

Preparation for Your Exam

If you are taking thyroid medications, a mineral supplement with iodine, or other medications or preparations that contain iodine, you may be asked to stop them for a time before this test. Check with your physician regarding the timing of your medications.

Please do not eat anything after midnight on the night before you are scheduled to take the radioactive iodine capsule.  If you are diabetic, please consult with your doctor before you change your diet or medications.  You may otherwise drink clear liquids for breakfast and take any non-thyroid medications prescribed by your doctor.  On the day of your exam, you will be able to eat normally two hours after you take the capsule.

During The Exam

For the scan, you will lie on your back on an imaging table with the camera positioned above you.  We will take several images of your thyroid. Each image takes five or ten minutes.  Then, a nuclear medicine physician will examine your gland.  We may then take additional images to look at a certain part of your gland in detail.  The imaging procedure will take about 45 minutes.

The uptake procedure measures the absorption of the radioactive iodine by your thyroid gland.  As you sit comfortably in a chair, a detector will be positioned several inches from your neck, and the amount of the radioiodine in your thyroid gland will be recorded.  This will take ten or fifteen minutes.

Safety Issues

Nuclear medicine procedures are very safe. The radioactive material is cleared quickly from your body.  With a normally functioning thyroid gland, the whole body radiation dose is 0.03 rem, which is less than most routine X-ray procedures.