A thyroid scan uses a radioactive tracer and a special camera to measure how much tracer the thyroid gland absorbs from the blood. The tracer can be swallowed or can be injected into a vein. It travels through your body, giving off rational signals. The camera "sees" the signals and can measure how much tracer the thyroid absorbs from the blood.

is quite rare and occurs in less than 10% of thyroid nodules. You might have one or more thyroid nodules for several years before they are determined to be cancerous