Thyroid Cancer Scan

Also available in PDF: Thyroid Cancer Survey

What is a thyroid cancer survey?

A thyroid cancer survey is a nuclear medicine scan to look for thyroid cancer tissue. It is a form of radiology, because radiation is used to capture pictures of the human body.

How does the exam work?

You will be given a small dose of radioactive material by mouth. This compound, called a tracer, collects in the thyroid gland and gives off beta and gamma rays. The gamma camera detects the rays and produces pictures of your thyroid gland and any other thyroid tissue.

How should I prepare for the exam?

• You must have had no X-ray exams involving iodine contrast (such as IVP or CT) in the last 2 to 3 months.
• Stop thyroid hormone medication (synthroid, cytomel, lexothyroxine, lithronine) 4 weeks before your exam. Check with your doctor.
• Stop your PTU or Methimazole thyroid medicine 4 days before your exam. Be sure to check with your doctor first.
• Do not consume any oral iodides (Lugol’s solution or vitamins containing iodine) for 2 weeks before your exam.
• You may be prescribed an oral diuretic to take. Check with your doctor.
• To must be on a low-iodine diet for 10 days prior to and throughout the study.
• Do not eat after midnight before your exam. You may drink water.
• Bring 2 forms of identification (ID).
• If you are a female of childbearing age, we will send you for a pregnancy blood test on Day 1 of the exam. Plan on 1 more hour to get the results from the pregnancy test. You must tell us if you are pregnant, even if you plan to terminate the pregnancy. Tell us if you are currently breastfeeding. You cannot continue to breastfeed after this exam.

How is the exam performed?

Thyroid Survey

1. Upon arrival, you will swallow a capsule containing tracer I-131.
2. You must fast for 2 more hours (except for water).
3. You will have pictures taken of your head and body with the Nuclear Medicine gamma camera, to look for leftover thyroid tissue and sites of thyroid cancer 3 days after you take the tracer capsule. Also, a measurement over your neck will be taken with another machine that detects radiation. You will lie on the table for about 1 hour while the scan is done.
4. You may need to come back on day 4 for additional imaging, if the doctor feels it is needed.
   5. Based on the results of this test, you may be treated with a higher dose of I-131.

Therapeutic Dose

1. If we need to treat you for leftover thyroid tissue and/or remaining sites of thyroid cancer, we will typically ask you to come back the day after your thyroid survey is done (day 4).
2. You will receive a higher dose of I-131 by mouth.
3. In most cases, this will require that you stay in the hospital from 2 to 4 days while waiting for your radiation levels to decrease.
   If you are admitted to the hospital, your room will be on the 6th or 7th floor.
4. Rooms for iodine patients are designed to shield against radiation. These rooms look very much like any other hospital room. Your door will be open, but for safety reasons, visitors will not be allowed past the doorway. Visitors may bring you items and may talk to you from the doorway.
5. The treatment has few side effects. You may have nausea that comes and goes, and you may feel some neck and salivary gland soreness. We will advise you on how to reduce these symptoms. If you are treated in the hospital, the medical staff will attend to any symptoms you might have.

Please review the radiation safety information/guidelines if you are receiving a therapeutic dose for Thyroid Cancer. Instructions for Receiving Radioactive Iodine Therapy for Thyroid Cancer Survey

What will I feel during the exam?

• Lying still on the exam table may be hard for some patients.
• Most of the tracer passes out of your body in urine, sweat, and saliva. The rest simply goes away over time.

Who interprets the results and how do I get them?