Thyroid scan Health Article

Definition

A thyroid scan is a nuclear medicine examination that uses a radioactive iodine tracer to see how well the thyroid gland is working.

Alternative Names

Scan - thyroid; Radioactive iodine screening test - thyroid; RAUI; Nuclear scan - thyroid

How the test is performed

You will be given a pill that contains radioactive iodine, and then you will wait as the iodine collects in the thyroid. The first scan is usually done 4 - 6 hours after the iodine pill is taken. Another scan may be taken 24 hours later.

Other scans may be done using a substance containing technetium.

After the radioactive iodine has been absorbed by the thyroid, you will lie on your back on a movable table with your neck and chest under the scanner. The scanner detects the location and intensity of the rays given off by the radioactive material.

During this part of the procedure, you must lie still to let the scanner get a clear image. A computer displays images of the thyroid gland.

How to prepare for the test

You must sign a consent form. You may be told not to eat after midnight the night before the exam.

Tell your health care provider if you are taking any medications that may need to be adjusted, such as thyroid medication and anything with iodine in it. Remove jewelry, dentures, or other metals, because they may interfere with the image.

How the test will feel

Some patients find remaining still during the test uncomfortable.

Why the test is performed

This test is done to check for:

• Hyperthyroidism
• Thyroid cancer
• Thyroid nodules or other growths

Normal Values

The thyroid appears the correct size, shape, and in the proper location. It appears an even gray color on the computer image.