Having your scan

This information tells you about having a PET-CT scan with us (following referral by your doctor) and aims to answer any questions you might have. On this page we aim to provide you with important information about the procedure and answer any questions you may have.

Please read this information carefully and if there are any questions or concerns then contact us on 01923 886311.

What is a PET-CT scan?

A PET-CT scan is a combination of two types of scanning technique in which a small amount of radioactive tracer (a type of fluid) is injected into a vein. This provides information about the anatomy (CT) and function (PET) of your internal organs. The scan tells doctors about the presence, location and severity of cancers. It can also be used for other conditions such as infection or inflammation and conditions that affect the brain. We are able to provide important information to help your doctor plan an appropriate treatment for you.

The PET-CT scanner is a large, quiet machine with a ring-like structure (see picture). You will need to be able to lie on your back on the scanning couch, which will move into the ring.

What are the risks of having a PET-CT scan?

The radioactive tracer has no documented side effects. The scan involves exposure to radiation in the form of gamma and X-rays. We ensure that the radiation dose you receive is both appropriate to address the clinical question being asked, and is as low as is achievable. A typical PET-CT scan radiation dose is equivalent to around 5 years of average background radiation which we all receive in the UK. The radiation dose for a PSMA PET-CT scan is typically about one quarter lower than that of other types of PET-CT scan.

The doctor who has referred you to us has judged that the risk of the radiation dose is outweighed by the potential benefits of the scan.

Before your scan appointment

Please inform us if the answer to any of the following is yes:

  • Are you diabetic?
  • Do you feel you need a chaperone?
  • Have you had chemotherapy within the past two weeks or radiotherapy within the past four weeks?
  • Have you had surgery within the past four weeks?
  • Have you had a recent infection or are you feeling unwell?
  • Are you pregnant, trying to get pregnant or breastfeeding?
  • Have you had previous MRI or CT scans that you have found difficult to tolerate or are you claustrophobic?
  • Do you have any additional needs (for example disabilities or mobility issues)?
  • Do you need hospital transport? If yes, this is something the team who referred you for your scan can help you with.
  • Do you need an interpreter?
  • Do you have any other appointments booked on the same day as this scan?
  • Do you weigh over 130 kg or 20 stone?

Unfortunately we’re unable to give sedatives or painkillers. If you do need something to calm your nerves or reduce pain, please speak to your doctor in advance and follow their advice closely. If you’ve taken a sedative, you must bring someone with you to your appointment.

Preparing for your scan

  • Drink at least two or three glasses of plain water in the four hours before your appointment. You may want to bring a bottle of water with you.
  • Do not exercise for 24 hours prior to your scan (for example, running, cycling, horse-riding, gym exercise but also holding a baby or knitting). You need to be as relaxed and rested as possible.
  • Please continue to take medications as usual unless otherwise instructed. If you have to take any medications with food, ask your doctor for further advice.
  • Please don’t bring children with you.

IMPORTANT: If you’re having an FDG PET-CT body or brain scan, don’t eat for 6 hours before your scan (this includes chewing gum, sweets or cough drops), and don’t drink anything other than plain water during this period. If you’re having a choline PET-CT scan or PSMA PET-CT scan, you can eat as normal and don’t have to stick to plain water. Your appointment letter tells you what kind of scan you’re having.

On the day

Please bring a dressing gown or warm, loose, metal-free clothing. You can take your usual medicines unless otherwise instructed. If in doubt, please contact us, especially if you are diabetic.

Avoid bringing valuables along to your appointment, as we don't have secure space to store them for you.

Please arrive at the Paul Strickland Scanner Centre reception at Mount Vernon Hospital (or at the GenesisCare reception desk if you are having your scan in Windsor) on time for your appointment because the radioactive tracer that we inject is ordered specifically for you and only works for a short time. If you are late we may not be able to proceed with your scan. If you are unable to attend or are going to be delayed, please telephone us at the earliest opportunity on 01923 886311
Sometimes, due to the complexity of both the scanner and the radioactive tracer that is injected, we can experience unforeseen technical difficulties which could mean we’re unable to scan you on the day. If this happens, we may need to cancel your appointment at short notice but we will rebook you for the first available convenient date.

If you’re having a scan of your brain, your injection and scan will take place in a darkened room.

Important information about your PET-CT scan

Sometimes, due to the complexity of both the scanner and the chemical tracer that is injected, we can experience unforeseen technical difficulties which could mean we’re unable to scan you on the day. If this happens, we may need to cancel your appointment at short notice but we will rebook you for the first available convenient date.

Bringing a friend, relative or carer?

You can bring a relative, friend or carer but they will have to wait in the waiting room unless you need their help with translation or have any special requirements.

Please do not bring children or pregnant friends/relatives with you or we may be unable to scan you.

Having your PET-CT scan

A member of staff will accompany you to a private room, ask you about your medical history and explain what will happen.

  • We will give you an injection of the radioactive tracer
  • We will ask you to relax in a resting bay for about an hour to allow the injection to be absorbed by your body.
  • Immediately before your scan, we will ask you to remove any metal items and empty your bladder.
  • We will then take you into the scanner room and ask you to lie on your back on the scanning bed.
  • The scan will usually take between 20 and 60 minutes. When the scan starts, the bed will move slowly through the scanner.
  • The radiographer or technologist will operate the scanner from the next room, where you can be assured that they can see and hear you at all times via a connecting window and intercom. The scanner is not noisy and having a scan is not painful.


Watch video in another language.

After the scan

If awaiting transport to collect you, please feel free to bring something along to eat and drink.

  • Once the scan is complete you are free to leave as soon as you feel ready. Keep at least one arm’s length away from others.
  • Avoid pregnant women and young children.
  • You may eat and drink as you normally would. Drink plenty of fluids and empty your bladder frequently.

Getting your results

One of our PET-CT specialists will analyse your scan. We will then send your report back to the doctor who referred you for your scan.

If you do not have another outpatient appointment arranged and you do not hear anything about the results within 3 weeks, we suggest that you telephone the referring doctor’s secretary for advice.

Your feedback

We strive to provide our patients with world-class scanning facilities, clinical excellence and opportunities to take part in innovative health research studies.

We welcome your feedback. Please complete one of our comments cards during your visit, which will help us improve our service.

Where to get more information


A Prostate Specific Membrane Antigen (PSMA) PET-CT scan specifically tests for Prostate Specific Membrane Antigen (PSMA), a type of protein that prostate cancer cells have more of. A PSMA scan may be able to detect prostate cancer earlier than other scans, which could benefit your treatment.

Everything you read on this page applies to a PSMA PET-CT scan too, however the radiation dose for a PSMA PET-CT scan is typically about one quarter lower than that of other types of PET-CT scan.

Directions and travel information

Information for patients having their scan in Northwood

Your scan will take place at Mount Vernon Hospital in Northwood. The address is Mount Vernon Hospital, Northwood.

See detailed travel information and map


Information for patients having their scan in Windsor

Your scan will take place at GenesisCare in Windsor. The address is 69 Alma Road, Windsor, SL4 3ES, Berkshire.

Get there by bus
The nearest bus stops to GenesisCare Windsor are Vansittert Road and Alma Road.

Get there by rail
The nearest railway stations to GenesisCare are Windsor & Eton Central and Windsor & Eton Riverside.

Get there by car
From A332/A308, take the exit at the roundabout onto Alma Road. Take the first turning to the left.

Parking arrangements
There’s free on-site parking.

Changes to travel and parking information
We have no control over parking and travel arrangements outlined in this booklet and they can change at any time without notice.
It’s a good idea to double check arrangements before your visit by ringing us on 01923 886315.

See detailed map