PET-MRI scan

What is a PET-MRI scan?

PET-MRI is a medical imaging device that performs both positron-emission tomography (PET) and magnetic resonance imaging (MRI) scans at the same time. PET is an advanced medical imaging examination used to evaluate the function of an organ or system in your body. MRI uses a magnetic field and radio waves to provide images of any part of the body from any angle.

The simultaneous use of PET and MRI gives your doctor a more detailed and enhanced imaging than either procedure does alone. This hybrid imaging technology aims to provide information on the causes, effects and development of various diseases.

How it works

During a PET scan, a radionuclide tracer is injected into the bloodstream. As radionuclide tracers usually accumulate in diseased tissues, PET scanners can use the radionuclide tracers to create multi-dimensional images of your body.

For the MRI scan, magnetic field and radio waves are used to generate images of the body. MRI scanners can produce detailed images of the body organs in thin sections and 3-dimensional views.

Why do you need a PET-MRI scan?

Your doctor may recommend a PET-MRI scan to do any of the following.

• Find and diagnose neurological disorders, abnormalities and complex malignancies such as cancers of the neck and pelvis
• Monitor how certain drugs travel through your body to determine proper bodily functions
• Monitor stem cells as they are maturing and developing into different body tissues

PET-MRI scans can offer you the following advantages:

• 50% less exposure to radiation compared to when PET scans are combined with computerised tomography (CT) scan
• More accurate diagnosis. PET-MRI scans can detect abnormalities in the brain which PET-CT scans miss in more than half of patients scanned
• Convenience of both PET and MRI scans completed in a single appointment

Who should not undergo a PET-MRI scan?

You should inform your doctor if you have any of the following:

• Metal or medical implants
• Tattoos
• Claustrophobia
• Pregnancy - during the first 12 weeks of pregnancy, doctors usually use other imaging methods, such as ultrasound, unless there is a strong medical reason to use MRI

They will discuss the risks with you.

What are the risks and complications of a PET-MRI scan?

A PET-MRI scan is a safe and painless procedure. There are generally no side effects from the imaging technology used.

How do you prepare for a PET-MRI scan?

In general, you are advised to avoid strenuous exercises or activities a day before the PET-MRI scan. You may also need to fast from food and drinks for a few hours before the PET-MRI scan.

What can you expect in a PET-MRI scan?

A PET-MRI scan is typically an outpatient procedure, so you can go about your day after the scan is completed.

Estimated duration

A PET-MRI scan takes up to 1.5 hours.

Before the procedure

You will be asked to:

• Change into a gown and remove all loose items such as jewellery, watch, keys, coins, smartphone, wallet and cards.
• Fill in a questionnaire about your medical history. Indicate on the questionnaire if you have any medical device or implant or aesthetic procedures performed such as permanent eyeliner, magnetic eyelashes and skin tattoo.

The radiographer will go through the questionnaire with you and explain how the scan will be performed.

You will also be given a small amount of radioactive tracer orally or through an injection. You will be asked to wait for up to an hour for the tracer to be absorbed.

• The medicine part of the tracer will get absorbed by diseased cells in your body.
• The radioactive part of the tracer emits radiation, which is detected using a special camera called a gamma camera.

During the procedure

You can expect the following during the procedure:

• You will need to lie on a scan bed. Headphones or ear plugs will be provided to you. There will be a call button in case you need to call the radiographer during the scan.
• The bed will slide into the PET-MRI machine. There will be intermittent knocking and humming sounds throughout the scan. This is caused by the changes in gradient fields in the magnet.
• You will need to remain still during the scan. Any body movement will cause blurry images and the scan will have to be repeated.
• You should not feel any discomfort during the scan. However, some patients may feel warm after some time in the magnet. This is normal but if it bothers you, you can press the call bell and inform the radiographer.
• When the imaging is completed, the bed slides out of the machine.

After the procedure

Unless otherwise instructed by your doctor, you will be allowed to carry on with your usual activities after a PET-MRI scan.

You will be instructed to drink at least 5 glasses of water to flush out the radioactive tracer.

Care and recovery period for PET-MRI scan

You should be able to go about your day as per normal after a PET-MRI scan.

If you experience the following symptoms after your scan, notify your nuclear medicine technologist or doctor immediately:

• Nasal congestion
• Itchy eyes
• Hives and rashes
• Sneezing
• Restlessness
• Tremors and pain
• Nausea and vomiting
• Dizziness