Positron Emission Tomography (PET) Scan

What is a Positron Emission Tomography PET scan?

A PET (positron emission tomography) scan is a type of nuclear imaging used to help diagnose conditions such as liver cancer. It involves a small injection of a safe radioactive tracer that highlights abnormal cells. Nuclear medicine is non-invasive and generally painless, aside from the injection.

PET scans are used to help diagnose liver cancer and assess for treatment response and metastatic disease (cancer that has spread outside of the liver).

Many imaging centres combine nuclear medicine images with computed tomography (CT) or magnetic resonance imaging (MRI) to produce special views. PET/MRI is an emerging imaging technology. It is not currently available everywhere.

Combined PET/CT scanners perform almost all PET scans today. These combined scans help pinpoint abnormal activity in the body and may provide more accurate diagnoses than the two scans done separately.

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How do I prepare for a PET scan?

Before your scan:

• let your treatment team know if you are (or could be) pregnant or if you are breastfeeding

• tell your treatment team if you are anxious about being in a confined/closed space (claustrophobic)

• let your treatment team know if you have diabetes
• ask if there are any food or drink restrictions.

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What happens during the PET scan?

A PET scan usually takes about 15 to 20 minutes, but expect to be in the imaging department for 2 to 3 hours.

A PET scanner is a large machine with a round, donut-shaped hole in the middle. It looks like a CT or MRI scanner. Multiple detectors inside the machine record the energy emissions from the radiotracer in your body.

Before the scan, a small amount of mildly radioactive material will be injected into a vein through a small plastic tube (cannula) in your arm. Cancer cells absorb more of this tracer than normal cells, so they appear brighter on the scan.

You’ll need to sit quietly for about 30 to 90 minutes to allow the tracer to spread through your body. In some cases, you may be asked to drink a contrast liquid that helps highlight your intestines (guts) for the radiologist interpreting the images.

Most nuclear medicine procedures are painless, aside from the brief pinprick when the needle for the radiotracer injection is inserted. You might feel a cool sensation in your arm as the tracer is injected, but significant discomfort or side effects are rare.

The scan itself doesn’t cause pain, though staying still for a long time may cause some discomfort. If you’re claustrophobic, you may feel anxious during the exam—let the staff know if you are worried.

Unless told otherwise by your doctor, you can return to normal activities after the scan. The small amount of radiotracer in your body will gradually break down and leave your system through urine or poo within a few hours or days. Drinking plenty of water can help flush it out more quickly. A nurse or doctor will give you any special instructions before you leave.

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What are the risks of a PET scan? 

Radiation

A PET scan is generally considered safe. The amount of radiation you’re exposed to is similar to what you’d receive from natural background radiation (this is the constant low-level radiation from natural sources in the environment) over about 3 years. The radioactive material used in the scan leaves your body quickly. After the scan, you may be advised to avoid close contact with pregnant women and babies for a few hours.

Allergic reaction

Allergic reactions to radiotracers are extremely rare and usually mild. Always tell the nuclear medicine personnel about any allergies you may have

Discomfort

The radiotracer injection may cause slight pain and redness. This should rapidly resolve.

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How much does a PET scan cost? 

If you have your PET scan done in a public hospital you will not pay for your scan. If you have a Medicare eligible referral from a specialist you should not have to pay for your PET scan at a private centre. If not covered by Medicare you may have to pay out of pocket costs and this will vary depending on the centre you go to. You should talk to your doctor about the best option for you. 

Reviewed Jan 2026