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PET/CT scanning - information for patients



PET/CT scans are undertaken at St Thomas' Hospital and the Cancer Centre at Guy's. Please remember to check your appointment letter to see where you are due at before you come for your scan.

  • What is a PET/CT scan?

    PET/CT stands for Positron Emission Tomography coupled with Computerised Tomography. It is a safe scan that produces a 3D colour image, containing precise information about the organs in your body.

  • Confirming or changing your appointment 

    When you receive your letter, you must telephone us to confirm your appointment on 020 7188 4988 or 020 7188 1493. If you do not, your appointment may be cancelled.

    If you need to change or cancel your appointment, please tell us as soon as possible by calling 020 7188 4988 or 020 7188 1493 so that we can offer it to another patient.

  • Before your appointment

    The scan will cause you to become radioactive for a short period of time so you must tell us in advance if:

    • you are pregnant (or think you may be)
    • you are breastfeeding
    • you are the primary carer of young children.

    You may drink water, but we ask that you do not eat food for six hours before your appointment.

    You may bring a family member or friend with you to the appointment, but during the scan they will have to stay in the waiting area. Please do not bring children with you.

    Most appointments last two to three hours.

  • What can I wear? 

    You may be asked to change into a hospital gown if you are wearing clothes with metal fastenings (e.g. zips) or buttons, as these show up on the scan.

    If you do not wish to change into a gown, then please make sure you don't wear clothes that may affect the scan.

    You may also be asked to remove head coverings, hairbands, jewellery, glasses and any metal objects. You may also need to remove any metallic dentures or hearing aids.

    Dental fillings will not affect the scan.

  • Will I need to have an injection?

    Yes, we will need to inject you with a tracer to help produce the scan. The tracer is usually a radioactive form of sugar, which stays in your body for several hours.

    The technologist will give you the injection through the cannula (a small plastic tube) in your arm. You will then need to rest in the cubicle so that the injection can circulate around your body and build up in your tissues. This is known as the up-take period. Different scans have different rest periods:

    • body scan - 60 minutes
    • brain scan - 30 minutes
    • heart (cardiac) scan - 30-60 minutes.

    While resting, you need to lie quietly and relax. You can sleep if you want to, or listen to music through headphones (please bring your own). You will not be allowed to read, because activity in the brain caused by reading can lead to increased up-take of radioactive tracer in the brain and affect the way the scan looks.

    You can drink water and go to the toilet if you need to. Before the scan begins, the technologist will ask you to empty your bladder. He or she will then direct you to the scanning room.

  • After your scan

    After your scan has finished, you can change back into your clothes. You can now eat and drink normally. Coffee and tea is available in the waiting room and there are a number of places that provide refreshments at St Thomas'.

    The results of your scan will usually be ready in one week. Occasionally we may need to do more scans. Your technologist will tell you if you need to return for further scanning.



Reception tel: 020 7188 4988
Bookings tel: 0207 188 1493

Email: gst-tr.PETCentre