Decorative image

PET scan

A PET scan shows where the nasal cancer is in the body. Read about what it is, how you have it and what happens afterwards.

Why you have a PET scan

A PET scan uses a mildly radioactive drug to show up areas of your body where cells are more active than normal. A PET scan can help show up nasal cancer and it can help doctors work out whether tissue is active cancer or not.

They are sometimes used to check to see if cancer has come back after treatment. You may also have a scan after treatment to make sure that there is no active cancer surviving in any scar tissue. It can be very difficult for doctors to tell scar tissue from remaining cancer after treatment. 

Where you have it

You’ll usually have a PET scan in the x-ray (radiology) department as an outpatient. These scanners tend to be only in the major cancer hospitals. So you might have to travel to another hospital to have one. A radiographer operates the scanner. It usually takes between 30 and 60 minutes.

Preparing for your PET scan

For most PET scans, you need to stop eating for about 4 to 6 hours beforehand. You can usually drink water during this time.

You might have instructions not to do any strenuous exercise for 24 hours before the scan.

Call the number on your appointment letter if not eating is a problem for you, for example if you’re diabetic. You might need to adapt your diet and sugar control, and your appointment time could change.

Some people feel claustrophobic when they‘re having a scan. Contact the department staff before your test if you’re likely to feel like this. They can take extra care to make sure you’re comfortable and that you understand what’s going on. Your doctor can arrange to give you medicine to help you relax, if needed.

What happens

Your radiographer might ask you to change into a hospital gown. You have to remove any jewellery and other metal objects such as hair clips. Metal interferes with the images produced by the scanner.

You have an injection of a dye called a radiotracer about an hour before the scan. You’ll have this injection through a small plastic tube called a cannula in your arm.

You need to rest and avoid moving too much during this hour. This allows the drug to spread through your body and travel to places where glucose is used for energy, like your brain.

When you arrive at the scan department

Your radiographer takes you into the scanning room. The PET machine is large and shaped like a doughnut.

You have most scans lying down on the machine couch on your back.

Once you’re in the right position, your radiographer leaves the room. They can see you on a TV screen or through a window from the control room.  You can talk to each other through an intercom.

Having the PET scan

The couch slowly slides backwards and forwards through the scanner. The machine takes pictures as you move through it. 

The scan is painless but can be uncomfortable because you have to stay still. Tell your radiographer if you’re getting stiff and need to move.

It’s not particularly noisy but you’ll hear a constant background noise.

When it’s over, your radiographer will come back into the room and lower the couch so you can get up.


After your PET scan

Your radiographer removes the cannula from your arm before you go home.

You can then eat and drink normally.

The radiation in the radioactive tracer is very small. Drinking plenty of fluids after your scan helps to flush the radiotracer out of your system.

The radioactive tracer gives off very small levels of radiation that go away very quickly. As a precaution, keep any time you spend within arm's length with pregnant women, babies or young children for 6 hours after your scan, as short as possible.

You need someone to take you home and stay overnight if you’ve had medicine to help you relax (sedative). You also shouldn’t drive, drink alcohol, operate heavy machinery or sign any legally binding documents for 24hours.

If you are travelling abroad within a week of your scan, it may be a good idea to take your appointment letter with you to show that you have had a scan. Most airports have sensitive radiation monitors which may pick up the trace of radiation following your test.

Getting your results

You should get your results within 1 or 2 weeks at a follow up appointment.

Waiting for test results can be a worrying time. You can contact your specialist nurse if you’re finding it hard to cope. It can also help to talk to a close friend or relative about how you feel.

For support and information, you can call the Cancer Research UK nurses on freephone 0808 800 4040. The lines are open from 9am to 5pm, Monday to Friday.

Contact the doctor that arranged the test if you haven't heard anything after a couple of weeks.

Possible risks

A PET scan is a safe test for most people. But like all medical tests it has some risks. Your doctor and radiographer make sure the benefits of having the test outweigh these risks.


Pregnant women should only have the scan in an emergency. There’s a risk that the radiation could harm the developing baby. Contact the department beforehand if you're or think you might be pregnant.


If you're breastfeeding, let the department know a few days before your appointment. They will let you know if you need to stop breastfeeding for a length of time after having the radioactive drug. You might need to store enough expressed milk for at least one feed.


Exposure to radiation from the radiotracer during a PET scan slightly increases your risk of developing cancer in the future. Talk to your doctor if this worries you. 

Bruising and swelling

You might get a small bruise around the area where they put the needle in. 

There's is a risk that the radioactive tracer will leak outside the vein. This can cause swelling and pain in your arm but it's rare.

Allergic reaction

Rarely, people have an allergic reaction to the radioactive tracer. This most often starts with weakness, sweating and difficulty breathing. Tell your radiographer immediately if you feel unwell.

Last reviewed: 
01 Dec 2017
  • Cancer and its management (7th edition)
    J Tobias and D Hochhauser occhhauser D
    Blackwell, 2015

Information and help

Dangoor sponsorship

About Cancer generously supported by Dangoor Education since 2010.