Positron Emission Tomography (PET) Scan
A PET scan produces detailed three-dimensional images of the inside of your body. It can clearly show any part of the body. This includes any areas that look abnormal.
What is a positron emission tomography (PET) Scan?
- A PET scan produces detailed three-dimensional images of the inside of your body. It can clearly show any part of the body. This includes any areas that look abnormal.
- PET scans are often combined with CT scans. This is called a PET-CT scan. This gives even more detailed pictures. Sometimes it can be combined with an MRI scan.
Important things to know
What does a PET scanner look like?
A standard PET scanner is a large, donut-shaped machine. It looks like a CT scanner. It has a short tunnel in the centre. You will be asked to lie on a table that then slides into the short tunnel.
Why do I need a PET scan?
A PET scan is often used to:
- See if your cancer has spread to other parts of the body.
- See whether prostate cancer has returned after treatment.
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Frequently asked questions (FAQs) about PET scans
What happens before a PET scan?
What do I need to do?
- You should get an appointment letter that tells you what you need to do before the scan. You may be asked to:
- Avoid food for about six hours before your scan. You will be able to drink water.
- Avoid strenuous exercise for about 24 hours before your scan.
- Wear loose and comfortable clothing. You may be able to wear these during the scan. Some hospitals may ask you to wear a gown.
- Avoid wearing jewellery and clothes with any metal attached for example, zips, belts or buttons.
What is a radiotracer?
- You will be given an injection of a radioactive substance.
This is called a radiotracer. To do this the radiographer will first put a small tube into the vein on the back of your hand or your arm. This is called a cannula. - They will inject the radiotracer through the cannula. The radiotracer will move around your body and collect in cancerous cells. After the injection, you will need to wait for one hour before your scan.
- You will need to keep as still as possible while you are waiting. Speaking and moving can affect where the radiotracer goes in your body.
What happens during a PET scan?
- The bed will pass into the scanner. You will need to lie on your back and keep very still. The scan takes 30–60 minutes.
Are there any special instructions I need to follow after my PET scan?
Yes, there are some special instructions you need to know.
- Do not have contact with pregnant women, babies or young children for about 6 hours after the scan.
- Drink plenty of fluids. This will help to flush any excess tracer through your kidneys and out of your body.
- You can eat and drink normally.
When will I get my test results?
- Your test results may take one-to-two weeks to come back. You may have a follow-up appointment with your doctor. They will tell you your results.
About this information
- This information was published in March 2023. We will revise it in March 2024.
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