I-123 Whole Body Scan Factsheet

Introduction

The thyroid gland is located at the front of the throat and has two lobes on each side of the windpipe. It makes chemicals called hormones that manage your child's growth and energy levels.

An Iodine-123 whole-body scan is used to:

check whether radionuclide therapy is needed – a treatment that delivers radiation directly to cancer cells
check for any functioning thyroid tissue or cancer
find any thyroid cancer that is still active, spreading or growing back
check the progress of I-131 therapy.

The Iodine-123 Whole Body Scan uses:

a Gamma camera – a large camera that measures radiation
radiotracer- a small amount of radioactive fluid that moves through the body.

The gamma camera takes pictures of the radiotracer moving through the thyroid tissue.

The scan is done over two days.

Before the scan

Your child’s treatment team will give you instructions on how to prepare for the scan. This includes:

a blood test before the scan to check for high thyroid-stimulating hormone (TSH) levels, which can signal a thyroid problem
a low-iodine diet for 1-2 weeks before the scan
information about which medications need to be stopped and when.

The risks of radiation and allergic reactions are very low. Let your child’s treatment team know if they have any allergies.

Talk to your child's doctor or treatment team if you have any concerns or questions.

Sedation

Your child must stay very still during the scan because movement can affect the images. If your child moves, the scan might need to be done again.

Some children may need sedation to help them relax and stay still. Sedation is a medicine that makes your child feel calm and sleepy.

If sedation is needed, your child will have to stop eating and drinking a few hours before the scan. Your child’s treatment team will give you more information about sedation and when to stop eating and drinking.

During the scan

The scan is done over two days. Your child will not feel anything during the scan, and the camera will not touch them.

Day 1

The first part will take about 30 minutes.

Your child will drink a small amount of liquid given in a syringe. The liquid is made of radiotracer, sodium bicarbonate, and sterile water.

The liquid can taste odd, and your child can have another cup of water to wash it down if needed.

Your child must wait 24 hours for the radiotracer to move through their body. You will go home and come back the next day for the scan.

Day 2

The scan will take around two hours to complete.

Before starting, your child will need to go to the toilet and do a wee to empty their bladder. If your child wears nappies, they will need to be changed into a new, clean nappy.

Generally, the steps are:

your child will lie on the scanning bed
a blanket with velcro straps may be used to help keep your child still
the camera will scan your child from head to toe, with each image taking about 10 minutes.

Your child will also have:

a single-photon emission computerised tomography (SPECT-CT) scan

This scan is used to take 3D pictures to see the organs better. It takes 30 minutes to complete.

a low-dose computed tomography (CT)

This scan uses X-rays to take a detailed picture of the inside of the body. It takes two minutes to complete. Because of the X-rays, parents and carers must leave the room for this scan.

After the scan

You can leave once the results are checked by a doctor or nuclear medicine scientist.

The results will be sent to your child’s doctor within a couple of days. You will need to schedule a follow-up appointment with your child’s doctor to discuss the results.

Management

Radiation

Your child will be exposed to a small amount of radiation during the scan. The benefits of finding and treating kidney problems are greater than the small risk of this low dose.

Allergic reactions

Allergic reactions to radiotracer are very rare and usually mild. Your child’s doctor will talk to you about any potential risks before the scan. Let your child’s treatment team know if they have any allergies.

Supporting your child during the scan

Scans can be uncomfortable for children. You can prepare your child by:

explaining to them why the test is needed in simple words
bringing along their favourite comfort objects, like a blanket, toy, or dummy
asking the treatment team about support from Child Life Therapy services.