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For patients

Positron emission tomography / computed tomography (PET / CT)

Do I need to confirm my appointment?

No, however if you can’t attend for some reason please let us know, this way we can give your appointment to another patient.

Please call us if any of these apply to you:

  • You have had chemotherapy within the last three weeks
  • You have had radiotherapy within the last three months
  • You have had surgery within the last three months
  • You have had a recent infection and are taking antibiotics
  • You are on steroids
  • You are pregnant, breast feeding, or have young children at home
  • You have had previous MRI or CT scans that you have found hard to tolerate or you are claustrophobic
  • You are a diabetic
  • You are unable to lie flat

Arriving for your appointment

Please allow plenty of time to get to the department as your radioactive tracer is specially ordered and scan times cannot normally be delayed.

Below is a video from Cancer Research UK, on what will happen when you have a PET / CT at Addenbrooke’s. Please note that you no longer have to get changed for the scan.

Watch: What is it like to have a PET Scan? | Cancer Research UK (opens in a new tab)

Preparing for your scan

  • Have nothing to eat or drink (apart from water) for 6 hours prior to your appointment time. You should drink plenty of plain water and water ONLY; No squash, tea, coffee etc.
  • Take all prescribed medications on the day of your scan as usual, unless otherwise instructed on your appointment letter.
  • Please leave all jewellery at home as we need to remove all metallic objects for the scan..
  • Please avoid strenuous exercise for 24 hours prior to your scan appointment, for example, running, cycling, horse riding and gym exercise.

What will happen on the day of the scan?

  • This will depend on what type of scan you are having. Our staff will fully explain the procedure to you when you arrive for your appointment.
  • A needle will be inserted into a vein in your arm, hand or foot. We will then take a small blood sample to check your blood sugar.
  • A small amount of a radioactive tracer will be injected through this needle.
  • You will then sit and relax quietly for 60 to 90 minutes before having the scan.
  • Please bring a book, magazine or a device to watch films / listen to music with you for this hour as you are on your own. If you are listening to a device please bring earphones with you as to not disturb other patients.
  • We will then ask you to lie on your back on the scanner table. Most scans last approximately 30 minutes.

How long will I be in the department for?

This will depend on what type of scan you are having but expect to be with us for between two and 3 hours. This includes preparation and scanning time.

Please note: the radioactive injection given to you is made off site and on occasions there can be delays and failures that may result in the cancellation of your scan.

Can I bring someone with me?

At present we would prefer for you to come alone. However if you have a carer or need assistance they are welcome to come along to the department, but will not be able to come through with you for the waiting time and scan.

Please do not bring children or pregnant friends / or relatives with you.

What are the benefits?

PET / CT combines two types of imaging in one scan. Your doctors get functional information from the PET scan as well as organ anatomy from the CT scan.

Are there any side effects or risks?

  • The scan involves an injection of a small amount of a radioactive tracer which will remain in your body for a few hours. This will not normally cause you any problems.
  • Very rarely there may be bruising at the site of the injection.

What happens after my scan?

  • You are free to go home.
  • You may eat and drink as normal.
  • Continue to drink plenty of fluids for the remainder of the day and empty your bladder regularly.
  • Please avoid close contact with pregnant women and young children for six hours after your scan.

When will I get my results?

  • Your results will be sent to the doctor who requested your scan.
  • Results are usually with your doctor within a week.
  • If you have a further appointment with your doctor, please let us know the date when you attend for your scan.


This scan forms part of a series of investigations your doctor will be undertaking. There is no equivalent scan to this study.