Nuclear Medicine Procedures: Thyroid Uptake and Scan
A thyroid uptake and scan assesses a patient's thyroid function. This two-part test is conducted over two days. The patient swallows a capsule containing a small amount of radioactive material. After the material has been absorbed by the thyroid gland, in about 18-24 hours, the patient returns for the thyroid uptake procedure.
Following the thyroid uptake, the patient is injected with another radiopharmaceutical and, after about 20 minutes, lies under a gamma camera, which makes images from emitted gamma radiation.
During the uptake procedure, the patient sits in a chair. For two minutes, a probe is placed next to the patient's neck, where the thyroid gland is located, to measure the radioactivity absorbed from the capsule. We then use the probe to measure radioactivity over the patient's thigh for two minutes to subtract background radiation.
Once the uptake is complete, a different radiopharmaceutical is injected in the arm. After 20 minutes, the patient lies under a gamma camera and we take three images of the thyroid. The entire procedure takes about one hour.
Before taking the capsule for the uptake, we determine if the patient has had any other test or is taking any medications that will interfere with the procedure. The patient may take nothing by mouth six hours before taking the uptake capsule, and should not eat for two hours afterwards. The first meal after taking the capsule must be a low carbohydrate meal.
The exam table's weight limit is 300 pounds. Patients who have had previous nuclear medicine exams may need to wait a few days before receiving a thyroid uptake and scan, depending upon the isotope received in the previous exam. Patients who are currently taking thyroid medication may need to stop for three days to six weeks, depending upon the medication. If a patient has recently had a CT scan with contrast, he or she must wait six weeks before having a thyroid uptake and scan.
Thyroid uptake doses are scheduled on the every hour from 7 a.m.-4 p.m. Monday through Thursday. Both the uptake and scans are performed at the main hospital campus only.
Patients with hypothyroidism (underactive thyroid) may need medication therapy. Those with hyperthyroidism (overactive thyroid) may require treatment with medication or radioactive iodine. Images from the thyroid scan are used to detect any "hot" or "cold" nodules and to correlate with the uptake exam.
Patients cannot be sedated to have a thyroid uptake and scan.
Frequently Asked Questions
Does a thyroid uptake and scan make me radioactive?
You receive a tiny amount of radiopharmaceutical. Usually, it loses its radioactivity within hours, and will pass out of the body within 24 hours.
Does a thyroid uptake and scan hurt?
Other than the minor discomfort of a needle stick, a thyroid uptake and scan is painless.
Who should not get a thyroid uptake and scan?
Generally, women who are pregnant or breastfeeding should not receive this procedure. It is safe for most other patients.