What is a PET scan?

A positron emission tomography (PET) scan is an imaging test that uses radioactive material to diagnose, monitor and treat a variety of conditions and diseases. Doctors use it to find tumours and diagnos heart disease, brain disorders and other conditions. A PET scan shows how the body is working, unlike other scans, which only show its structure.

PET scans use a small amount of radioactive tracer glucose. A radioactive tracer is a small amount of radioactive substance used to help create images. Fluorodeoxyglucose (FDG) is a common tracer used. FDG is a simple sugar (glucose) that has been radiolabelled — this means that when it is injected into your body, a scanner can see where this sugar is taken up.

Your tissues use sugar for energy. Active cells take up more sugar, so they appear brighter on the scan. They are known as 'hot spots' and may indicate a tumour.

When is a PET scan used?

PET scans are used for many reasons, including helping your doctor:

• find tumours
• check if cancer has spread or returned
• monitor how a tumour is responding to treatment
• diagnose and assess heart disease
• evaluate brain disorders, including epilepsy, to see if surgery may help

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Is a PET scan safe?

PET scans are considered safe. The radioactive tracer remains in your body for a short time.

The radiation dose is small — similar to several years of natural radiation from the environment.

Allergic reactions can occur but are uncommon and usually mild.

Let the staff know if you are pregnant, might be pregnant or are breastfeeding.

Where can I get a PET scan?

PET scans are done in hospitals and specialised radiology centres. You will need a referral from your doctor.

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What happens during a PET scan?

The scan itself takes about 15 to 20 minutes, but you will need to be in the PET imaging department for a few hours.

Before the scan

Before the scan, you should:

• ask about any food and drink restrictions before your scan
• bring any previous x-rays or other radiology images you have
• let staff know if you'r breastfeeding or might be pregnant
• tell the staff if you hav diabetes
• tell the staff if you are likely to feel anxious about being in a closed space (claustrophobia)

Before the scan

After arriving at the hospital or radiology centre:

• you will change into a gown and remove all metal and jewellery items
• your blood sugar levels will be checked
• staff will insert an intravenous line (IV drip) into a vein in the back of your hand or arm
• the radioactive tracer will be injected into your vein through the intravenous line

Waiting period

You will then rest quietly in bed or a chair for 90 minutes. For some scans, you may be given contrast material to drink — this is a liquid that helps make images clearer and takes some time to move through your body. You will be able to empty your bladder before the scan starts.

During the scan

You will lie down on a bed that slides into the 'ring' of the PET scanner, which takes pictures of the inside of the body. Once in the PET scanner, you will be asked to remain as still as possible while the scans are being done.

The scan usually does not take more than 20 minutes.

After the scan

After the scan, staff will check the images. They will remove your intravenous line. You should drink plenty of water to flush out the radioactive tracer. If you are breastfeeding, you will be given specific instructions about when to resume breastfeeding.

A specialist will examine the scans and write a report for your doctor, who will explain the results to you.

What does a PET scan feel like?

A PET scan is painless. During a PET scan, you will have to remain still for a long period of time.

If you are stiff, uncomfortable or claustrophobic, tell the staff as support is available.

Are there side effects or complications of a PET scan?

A PET scan involves a small amount of radiation exposure, but the amount of radiation is low and considered safe for most people.

Allergic reactions to the radioactive tracer are uncommon, as it is given in very low doses. Reactions to contrast material may include:

• flushing
• nausea and vomiting
• mild itching
• headache

Severe reactions are rare. In some cases, a biopsy may still be needed to confirm or rule out disease activity seen on a PET scan. A biopsy is a small tissue sample taken for testing.

Are there alternatives to a PET scan?

Depending on what your doctor needs to investigate, alternatives may include:

• computed tomography (CT) scan
• magnetic resonance imaging (MRI) scan
• x-ray
• ultrasound

These tests can show if you have or don't have a disease but cannot show how active the cells are. Your doctor will recommend the best test for your situation.

Resources and support

For more information about PET scans, when they are used and how they are done, see th Cancer Council website or the Peter MacCallum Cancer Centre website.

The Australian Government has a list of PET units in Australia.

Our Mob and Cancer has information about different tests for cancer, including PET scans.

Call healthdirect on 1800 022 222 at any time to speak to a registered nurse (known as NURSE-ON-CALL in Victoria) for more information and advice.