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18F-FDG PET-CT scan?

Patient information A-Z

1. What is a PET-CT scan?

PET-CT (Positron Emission Tomography and Computerised Tomography) is a scanning method that allows us to see how organs are working. PET-CT helps us identify organs or tissues that are not working normally. The body is imaged following the injection of a radioactive tracer (most commonly 18F-FDG, a slightly radioactive form of sugar). This provides important information about many conditions affecting different organs and the images allow your doctor to plan your treatment more effectively.

Alliance Medical have the national PET-CT contract for England and we are subcontracted by Alliance Medical to carry out PET-CT scans on their behalf.
Alliance Medical have the national PET-CT contract for England and we are subcontracted by Alliance Medical to carry out PET-CT scans on their behalf.

2. Do I need to confirm my appointment?

No: If you are unable to attend or have any other queries then please telephone the department. This way we can give your appointment to another patient if appropriate. The tracer we use is also extremely expensive and cannot be reused. It has been specially ordered for you. Please help us to conserve valuable NHS resources.

Your scan will take place in the PET-CT department of Addenbrooke’s Hospital. Please allow plenty of time to get to the department as your radioactive tracer is specially ordered for you. The tracer is produced off-site and delivery can sometimes be delayed because of production or transportation issues. It is vital that you arrive on time for your appointment as the radioactivity has a very short shelf life. If you are late for your appointment we may not be able to proceed with your scan.

Please inform us if any of the following apply:

  • You have had or are expecting chemotherapy within three weeks of your appointment.
  • You have had radiotherapy within the last three months.
  • You have had surgery within the last three months.
  • You have had a recent infection.
  • 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 taking oral steroids.
  • You are a diabetic.
  • You are aware healthcare practitioners have problems taking blood samples from you.
    • have any disability or special needs requiring ramp access
    • weigh over 100kg (16 stone)
    • have any difficulty lying flat for 20 minutes
    • have any other appointments on the same day.

3. Preparing for your scan

  • Have nothing to eat or drink apart from water for six hours prior to your appointment time. Check your appointment letter.
  • You should drink plenty of plain water. Please avoid flavoured water.
  • 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. We suggest wearing something loose and comfortable. If required, a hospital gown can be provided for the scan.
  • Please avoid strenuous exercise for 24 hours prior to your scan appointment, for example, running, cycling, horse riding or gym exercise.
  • You do need to be able to lie flat for this scan. Please inform us if you do not think you can manage this.
  • If you are a diabetic please contact us for further information.

4. 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 small needle will be inserted into a vein in your arm, hand or foot.
  • Your blood glucose will be checked. We need your blood sugar to be at a fairly low level, which is the reason for the diet. If high blood sugar levels are detected, your scan will need to be rescheduled.
  • A small amount of a radioactive tracer will be injected through the needle.
  • You will then lie and relax quietly for 60 to 90 minutes before having the scan.
  • You will be asked to empty your bladder just before the scan begins.
  • We will then ask you to lie on your back on the scanner with your arms placed above your head.
  • You may have another injection of an X-ray dye during the CT scan.
  • Most scans last from 25 to 45 minutes.

5. 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 three hours. This includes explanation, preparation and scanning time.

6. 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 frequently.
  • Please avoid close contact with pregnant women and young children for six hours after your scan.

If you are breastfeeding, we recommend that you:

  • Express and appropriately store at least one feed before your appointment
  • Breastfeed your child before your appointment
  • Express as much milk as you can in the 2 hours after your scan and discard the milk
  • Ideally, have someone else bottle feed the stored milk to your child until the end of your six-hour contact restriction

7. Can I bring someone with me?

Any friends or relatives bringing you to your appointment will not be allowed to stay in the unit due to limited waiting room space. Only an essential carer or interpreter is permitted. Please note that during your scan, they will be asked to wait outside the scan room due to the limited space.

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

Ensure that you adhere to current Trust COVID-19 guidelines regarding the attendance of appointments.

8. 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 to check if your organs and tissues are functioning normally.

9. 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 radiation can cause cell damage that can, after many years or decades, contribute to the development of cancerous cells. This procedure carries only a very small chance of this happening to you.
  • Very rarely there may be bruising at the site of the injection.
  • If you have the CT dye injection you may get a warm flush feeling during the injection.
  • Your doctor will have considered the risks and benefits of having this test before referring you to us. The benefits of the test outweighs the potential risks.
  • The main side effect people find is boredom during the relaxing stage!

10. 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 or two, often much sooner.
  • If you have a further appointment with your doctor please let us know the date when you attend for your scan.

11. Alternatives

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

12. Contacts/Further information

  • Telephone 01223 349222

We are smoke-free

Smoking is not allowed anywhere on the hospital campus. For advice and support in quitting, contact your GP or the free NHS stop smoking helpline on 0800 169 0 169.

Other formats

Help accessing this information in other formats is available. To find out more about the services we provide, please visit our patient information help page (see link below) or telephone 01223 256998.

Contact us

Cambridge University Hospitals
NHS Foundation Trust
Hills Road, Cambridge

Telephone +44 (0)1223 245151