What is an FDG PET-CT Scan?

A PET-CT scan combines a PET scan and a CT scan.

PET stands for Positron Emission Tomography and is a medical imaging technique where the patient is given an injection containing a small amount of radioactive tracer prior to the scan to assess body function. 18F-Fluorodeoxyglucose, more commonly known as 18F-FDG, is the most commonly used radioactive tracer in PET and behaves as ordinary glucose when injected into the body.

CT stands for Computed Tomography and uses x-rays to produce images of different organs within the body.

By combining these two techniques, we are able to provide important information to help your doctor design the best treatment plan for you.

All PET-CT scans are carried out at 77 Wimpole Street, London.

What should I do before the scan?

You will need to fast for six hours prior to your scan. If you are an insulin-controlled diabetic, only fast for four hours following administrating your insulin.

Avoid strenuous physical exercise for 24 hours before your appointment, which includes the practice of any kind of sporting activity.

What happens during the scan? 

First, you will be given an injection of the radioactive tracer. Once the tracer has been administered you will need to rest comfortably for around 60-90 minutes while the injection is absorbed into your body. 

After the rest time, you will be scanned which will last between 15-20 minutes, depending on the type of scan required.

What should I do after the scan?

Once the scan is complete, you will be able to return home and resume your normal activities and diet. 

You are advised to: 

  • Drink plenty of water (4-5 glasses); this will help flush the tracer out of your system. 
  • Limit close contact with infants and pregnant women for the first five hours after your scan to avoid exposing them to any radiation. 

There are currently no related conditions associated with this test.

Royal Brompton nuclear medicine

Level 3, Chelsea Wing, Sydney Street


Monday to Friday, 9am to 5pm

Tel: 020 7351 8666 / 9
Fax: 020 7351 8668
Email: nmadvice@rbht.nhs.uk

Patient advice line: 020 7351 8667

If you have any questions or concerns about the scan please call our patient advice line.

It is an answerphone service – leave a message and we will call you back within 24 hours.

Department head

Kshama Wechalekar