Information for patients > Services > PET-CT Scan
PET-CT Scan
Information for patients
It is perfectly understandable to be apprehensive when you arrive for an investigation, but staff at all our sites are kind, friendly, informative and helpful and will help you to feel relaxed and calm. The information below should give you a reasonable idea about how to prepare for your particular type of investigation.
Frequently Asked Questions (FAQs) - PET-CT Scan
What is a PET-CT Scan used for?
How do I prepare for a PET-CT scan?
What happens immediately before the PET-CT scan?
How long is a PET-CT scan and is it uncomfortable?
Any handy links to find out more about PET-CT scans?
PET stands for Positron Emission Tomography. This is a fairly new type of scan developed in the 1970s. More recently PET scanners have been combined with CT scanners so it can show how body tissues are working, as well as what they look like.
What is a PET-CT Scan used for?
PET-CT scans are mostly used to diagnose and stage cancers. They are sometimes used to image the heart and brain. PET-CT is used in many but not all types of cancer. It is also used to show how well chemotherapy or radiotherapy have worked and to show the difference between scar tissue and active cancer tissue when the results of other tests such as CT and MRI are uncertain. As with other scans, PET scans are not right every single time; but they can greatly increase the certainty of a diagnosis and help doctors decide on the best course of action.
How do I prepare for a PET scan?
For some PET-CT scans you may need to eat nothing for 4 to 6 hours before your appointment time and only drink water. If so, you will be informed accordingly. For other scans there will be no preparation at all. Unless you are told otherwise, always take any prescribed medications as usual.
If you are diabetic we will need to know as insulin and glucose levels can affect how well the scan performs.
What happens immediately before the PET-CT scan?
With a PET-CT scan you first have an intravenous injection of a small amount of a radioactively labelled substance called a tracer. It only stays in the body for a few hours. The most common tracer is a radioactive version of glucose. When this is injected into your body it travels to places where glucose is used for energy. It shows up cancers because they use a lot of glucose. It will also be taken up by normal tissues which use glucose for energy, for example the brain, and as a result of other abnormalities such as infection. Indeed PET-CT is sometimes used to find infections.
After you have the injection you rest for about an hour. This allows the radioactive tracer to spread through the body to the areas we wish to see. Resting reduces glucose uptake in the muscles. You may be asked to remain silent during this hour to prevent uptake in the vocal cords.
How long is a PET-CT scan and is it uncomfortable?
The scan itself takes 30-40 minutes. The scan produces an image of the radioactive tracer in the body which can be combined with the CT image. It is important that you are comfortable as it is important to lie as still as possible while the scan is being done. If you begin to feel unwell or want some help, you will have a buzzer that you can press to get attention. The staff doing the scan will be able to see you at all times. After your scan you should feel fine and be able to resume your normal diet and activities. You will be encouraged to drink plenty to wash out the tracer
For the patient, PET-CT scans are very safe. You do have a radioactive injection, but this is a small amount and it decays and is removed by the kidneys very quickly. These days, some doctors tell PET-CT scan patients that they should not have close contact with pregnant women, babies and young children for a few hours after their scan. If you are breast feeding, you have to express enough milk beforehand to get your baby through the first 6 hours after the scan. This isn't because there will be radiation in the milk. It is because the mother shouldn't be holding the baby closely during the time the radiation is in her body. Some doctors recommend you get someone else to feed the baby for 24 hours, although it is safe for you to express more milk for those feeds from 6 hours after the scan.
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