Positron Emission Tomography (PET) Scan

What is a PET scan?

Positron emission tomography (PET) is an advanced medical imaging examination that provides detailed information on the function of an organ or system in your body.

It is combined with an anatomical technique such as a computed tomography (CT) or magnetic resonance imaging (MRI) scan at the same time. These techniques allow your doctor to:

• Assess how functionally active an organ or tissue is in conjunction with its appearance.
• Detect abnormalities even before an organ has changed from its normal shape

PET scans are often used to evaluate and diagnose cancers, neurological (brain) disorders, and cardiovascular (heart) diseases.

A PET-CT or PET-MRI scan can provide more information in staging cancer than MRI or CT scans alone. These scans can also show how well a cancer treatment is working. For the heart, a specialised rubidium PET-CT scan can determine whether the heart muscle is receiving sufficient blood flow under different conditions.

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.

Most PET scanners are combined with CT scans. This allows the structural information provided by CT images to be combined with the PET’s functional information.

Images with a colour map from your PET scan will be prepared for you to discuss with your specialist doctor.

Why do you need a PET scan?

A PET scan can:

• Measure vital functions, such as blood flow, oxygen use and blood sugar (glucose) metabolism.
• Identify organs and tissues that aren’t working as they should, or are inflamed.
• Detect cancerous tumour cells to help gauge cancer spread (metastasis).
• Evaluate how well a cancer treatment is working.

A PET scan can find cancers before other imaging techniques such as CT and MRI scans. It can also help your doctor to determine where cancer might be spreading.

When do you need a PET scan?

Your doctor may recommend a PET scan to:

• Detect or stage possible cancer
• Determine if vital organs such as the heart are receiving adequate blood flow to critical areas
• Investigate suspected infection or inflammation in your body, including your organs and bones
• Investigate an organ abnormality
• Follow up after cancer treatment

A PET scan can further assist in the planning of surgery for epileptic seizures by showing which part of your brain is responsible for epilepsy.

It is also used to assess Alzheimer’s disease and Parkinson’s disease because the resulting images can show the areas of the brain that are not functioning normally. Early detection of these neurological disorders can lead to more effective treatment.

What are the risks and complications of a PET scan?

A PET scan is a safe and painless procedure. However, if you suffer from claustrophobia or the fear of enclosed spaces, you may be concerned about entering the machine.

Please discuss this with your doctor so that we may tailor optimal care for you.

How do you prepare for a PET scan?

Before your PET scan, you should tell your healthcare provider:

• If you have claustrophobia (fear of enclosed spaces).
• If you have had a bad allergic reaction in the past.
• About your health condition like diabetes or pregnancy.
• About the medications and supplements that you are taking.

In general, you are advised to avoid strenuous exercises or activities a day before the PET scan. You may also need to fast a few hours before the PET scan.

What can you expect for a PET scan?

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

Estimated duration

A PET scan takes around 30 minutes but may take longer if special views or MRI scans are required.

During the procedure

You must remain still throughout the procedure as movements can cause blurring in the resulting images.

The technologist will give you instructions, such as when to hold your breath and when to remain still. During the scan, you may hear buzzing and clicking sounds.

After the procedure

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

You will be instructed to drink at least 5 glasses of water.

Care and recovery after a PET scan

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

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

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