Iodine-123 whole body thyroid cancer imaging

What is this test?

This test is done to find out if you have active thyroid tissue and/or thyroid cancer tissue. It helps your doctor decide if treatment will be needed. People most often need treatment after thyroid cancer surgery.

Your appointment

If you make any changes to your appointment before your appointment please call Registration at 1-866-309-0832. This will help to prevent any delays and the need to reschedule your test, as many radiology services need a pre-authorization.

Take Elevator H or I to Level 3 Nuclear Medicine Center. It is between elevators H and I.

Please call Nuclear Medicine at 1-319-356-1911 if you:

  • Have questions
  • Need to cancel your appointment
  • Are unable to do the prep below or think you may be pregnant
    • You may not be able to have the test, or it may need to be rescheduled.

Getting ready for your test

Before your test, tell your doctor or nurse if:

  • You are pregnant or think you may be pregnant, or if you are breastfeeding.
    • You may have to give a urine sample if a pregnancy test is needed. 

Skin Prep

  • Do not use iodine tincture two weeks or betadine one month before your test.


  • Two weeks before your test, start a low iodine diet.
  • Do not eat or drink for four hours before or two hours after your thyroid test. You may drink water.
  • If you have any other test today where you are told not to eat or drink for a longer amount of time, follow those instructions.


  • Stop taking dietary supplements with iodine, such as vitamins, minerals or kelp, at least one week before your test.
  • Talk to your doctor about how to take your thyroid and other medicines. If you are getting Thyrogen injections, you can take your thyroid medicines. Often you will stop these medicines before your test:
    • Synthroid six weeks before and start taking Cytomel as prescribed by your doctor.
    • Cytomel two weeks before.

What to expect

For this test, you will come to Nuclear Medicine for two visits, two days in a row. If your doctor chooses to use Thyrogen injections rather than stopping your thyroid medicine, you will get one injection the day before your first visit and one the day of your first visit.

  • The thyroid cancer imaging requires 60 minutes to start on the first day in Nuclear Medicine and 90 minutes in Nuclear Medicine to complete on the next day. 

Day 1

  1. Go to your primary clinic for lab studies. You will have a:
    • Pregnancy test if you are of child-bearing age (11 to 54)
    • TSH lab if you have been taken off your thyroid medicines
  2. Go to Nuclear Medicine at your scheduled time after your lab studies are done. You will take capsules with a diagnostic dose of Iodine(I)-123. There is no reaction to the I-123 dose. This will take about 60 minutes.

Day 2

  1. Go to Nuclear Medicine for the I-123 whole body scan. The whole body scan is done using a special machine called a gamma camera. The camera:
    • Does not emit any radiation.
    • Will be close to your body while the pictures are taken.

Often people need treatment with radioiodine I-131 therapy after the I-123 scan. Often the I-131 therapy can be given the same day your thyroid whole body exam is done. 

Last reviewed: 
August 2018

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