Positron Emission Tomography/Computed Tomography is a diagnostic tool used mainly in oncology staging. It’s also used widely in planning surgery and treatment.

PET CT is used to diagnose a wide range of conditions. Visit our Scan Glossary for details of conditions scans are used for.

Having a PET/CT scan

Important things to tell us before having a PET/CT scan

It’s important that you tell us before the scan if you:

  • are diabetic
  • are (or might be) pregnant, breast feeding or in contact with young children.
  • weigh more than 100kg.
  • are booked for other appointments on the same day.
  • suffer from allergies or asthma.
  • have ever received chemotherapy or radiotherapy.
  • have a follow up appointment with your Doctor.

PET/CT scanner

  • Unless we tell you otherwise, please don’t have anything to eat or drink, except water, for six hours before your appointment.
  • In fact, it’s quite helpful if you drink 4 or 5 glasses of plain water.
  • Please confirm your appointment if requested to do so prior to your scan and arrive in plenty of time
  • You’re welcome to bring a friend or a relative with you – female companions must not be pregnant– but for safety reasons we won’t normally allow them into the examination room. It’s really important that you arrive by the time we tell you. We’ll need to give you an injection (see below – Preparation) which has an extremely short shelf life and if you’re late we might not be able to use it – and your appointment will have to be cancelled.
  • We may give you a medicine to enhance the scan results. If we think this is necessary, we’ll discuss it with you before your scan and you will not be able to drive afterwards so you will need to make arrangements for someone to collect you.
  • Once you’ve checked in at reception (don’t forget to bring your appointment letter), a member of the scanning team will meet you, explain the procedure, go through your safety questionnaire with you
  • We might ask you to get changed. We’ll give you a container to keep your clothes and personal belongings safe.
  • You’ll be looked after by the scanning team throughout the procedure – they will explain what’s happening and will be there if you experience any discomfort.
  • You’ll have the opportunity to ask any questions.
  • We’ll need to inject you with a radioactive tracer; it’s a minor injection (no worse than having a blood test);
  • After the injection, you’ll need to lie still without talking for around an hour to allow the tracer to be absorbed into your body.
  • Then we’ll ask you to empty your bladder, following which you’ll be ready for the scan.
  • The technician operating the scanner will be able to see and hear you throughout the procedure.
  • We’ll ask you to lie down on the scanner bed and we’ll make sure you’re comfortable so you can stay as still as possible. You won’t feel anything.
  • Most scans take between 30 minutes and one hour.
  • For safety reasons, we don’t normally allow anyone accompanying you to come into the examination room whilst the scan is in progress.
  • Do not drive if you have been instructed not to. Drink plenty of fluids – this will help flush the tracer from your body.
  • We strongly recommend that you don’t have close contact with any pregnant women or young children for eight hours following the scan.
  • A Consultant will examine the images shortly after your visit and send a report to your Doctor or Consultant, normally within a few days.
  • For ethical and professional reasons, we cannot discuss results with you. Only your Doctor or Consultant can do this.

What is a PET Scan?  

A Pet scan is a scan that can test for certain diseases. It involves an injection with a tracer that allows us to see how organs and tissues are working.


How long does it take?

The total length of time for an appointment is 2.5 hours due to the preparation involved before having the scan. The scan itself takes 20-25 minutes or 45 minutes for a full body scan.


Do I need to fast?

Yes you will need to fast from midnight the night before. It is important to contact staff and advise them if you are diabetic as different fasting guidelines may apply depending on the time of your scan.


What should I expect when there?

We will go through your medical history, check your weight and height and give you a gown to wear. We will give you an injection with a tracer and ask you to relax for up to an hour before taking you in for your scan. Once completed we will give you time to get dressed before offering you a cup of tea/coffee and a light snack.


What is FDG?

It is a radioactive isotope that targets specific cells that are in a fasting state.


Am I radioactive after the scan/ how long am I radioactive?

You will be radioactive for up to ten hours after the scan, we ask that you please keep your distance from pregnant women and small children during this time.


What does being radioactive mean?

You are emitting radiation to the people around you.


How long does it take to get results?

It is dependent on other investigations you may be having but it is reported on within 48 hours, however more complex studies can take longer.


Who gets the results?

The results get sent to your referring doctor.

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