PET CT scan

Seeing structure and activity together

A PET CT scan combines a CT scan, which uses X-rays to create detailed images of your body, with a PET scan from nuclear medicine.

Before the scan, a small amount of radioactive glucose is given through a vein. Cells that are more active than usual take up more of the tracer, allowing the PET scan to show changes in metabolic activity. The CT scan shows exactly where those changes are happening.

The two sets of images are then combined, giving your doctor information about both the structure of your body and how its cells are functioning.

What PET CT can help with

• Diagnose and stage cancer
• Help decide whether surgery may be an option
• Help plan the most appropriate cancer treatment
• Show how well treatment is working
• Help identify where a cancer first started
• Check whether cancer has returned
• Distinguish active cancer from scar tissue after treatment
• Locate infection in the body
• Identify inflammation in the arteries

Preparing for your scan

You’ll receive specific preparation instructions with your appointment. It’s important to follow these carefully so the scan produces useful images.

Generally, you should not eat for six hours before your appointment, although you can drink water. You should also avoid strenuous exercise for 24 hours before the scan.

For the day before your scan, you may be asked to avoid foods such as rice, bread, potatoes, pasta, noodles, processed foods, biscuits, chocolate, sweets, and pizza, as well as drinks containing caffeine such as tea, coffee, and cola.

Foods listed as suitable alternatives include fruit, vegetables, fish, meat, eggs, milk, yoghurt, cheese, nuts, and seeds.

Keep taking your prescribed medicines unless your doctor or the scanning team tells you otherwise. If you have diabetes, contact the department a couple of days before your appointment, as you may need advice about your diet or blood sugar control.

Radiation, pregnancy, and breastfeeding

PET CT uses both X-rays and a radioactive tracer. The amount of radiation from the tracer is small and it loses its radioactivity quickly. Drinking plenty of water after your scan helps your body clear it.

For the rest of the day, avoid prolonged close contact with pregnant women, babies, and young children.

Please don’t bring children under 16 or anyone who is pregnant to the scanning department. A friend or relative can come with you, but they won’t be able to stay with you once the radioactive tracer has been given.

Tell the team before your appointment if you are or could be pregnant. PET CT during pregnancy is rare and would only be considered when your doctors believe it is essential.

If you’re breastfeeding, contact the department a few days before your appointment. The team will tell you whether you need to stop breastfeeding temporarily and for how long, and you may need to store enough expressed milk for at least one feed.

If you receive a sedative for your scan, you must not drive for the rest of the day. You’ll need someone to take you home.

Getting your results

A nuclear medicine specialist reviews your scan and prepares a report for your referring doctor, who will discuss the results with you.

Results may take up to two working days to become available. If your doctor needs them urgently, this can be noted on the scan request.