10123 Pet Scan

Overview

A PET scan (positron emission tomography) is a painless imaging test that shows how well parts of your body are working. A very small amount of a safe radioactive tracer is put into your body, usually through a vein in your arm. The tracer travels to the areas your doctor wants to look at, and a special scanner picks up the tiny signals it gives off. The scan builds pictures that show which tissues are more or less active than normal. Many people have a PET-CT scan, which is a PET scan and a CT scan done on the same machine at the same time. The CT part shows the shape of your organs and the PET part shows how they are working, so doctors can line the two pictures up.

Yes. PET scans are a common and well-established test in hospitals around the world. They are used most often in cancer care, in heart problems, and in some brain conditions, but they are only done when the information will actually help your care.

PET scans can be done at any age, from young children to people in their 90s. They are more often needed in older adults, simply because cancer, heart disease and some brain conditions become more common with age. Your doctor will only suggest a scan if it is likely to help answer a question about your health.

Symptoms

Common symptoms

• A PET scan does not cause symptoms, because it is a test rather than a disease. These are the kinds of problems or findings that may lead your doctor to suggest a scan:
• A known or suspected cancer, or finding out whether a cancer has spread
• Checking how well a cancer is responding to treatment, or whether it has come back
• Unexplained weight loss, fevers or tiredness that tests so far have not explained
• Chest pain or breathlessness being checked for problems with the heart muscle or its blood supply
• Seizures or memory problems being looked at for certain brain conditions
• A lump or a change on another scan that doctors want to understand better

Symptoms in children

• Children sometimes need a PET scan, usually to look at cancers that are more common in childhood. The scan works the same way as in adults.
• Young children may need a mild sedative or a short general anaesthetic so they can lie still, and a parent or carer can usually stay close by until that happens.
• Children get a smaller, carefully measured dose of tracer, based on their weight.
• Your child's team will explain the day in simple words beforehand, and play specialists can help if the hospital has them.

Symptoms in older adults

• Older adults have PET scans safely, but the team may check a few extra things.
• If you have diabetes, your blood sugar level may need to be checked and steadied before the tracer is given, because high blood sugar can spoil the pictures.
• If you have kidney problems, the team will make sure you can clear the tracer well and will encourage you to drink plenty of water afterwards.
• If lying still for a while is hard because of arthritis or back pain, tell the team in advance. They can use cushions and plan rest breaks.
• Bring a list of all your medicines, including anything you buy over the counter, so the team can plan around them.

Causes

Main causes

• A PET scan is not caused by anything; it is done for a reason. Common reasons include:
• Finding out whether a growth is cancer and whether it has spread
• Planning treatment, such as surgery or radiotherapy, by showing exactly where active tissue is
• Checking early on whether a treatment is working, so it can be changed if needed
• Looking at the blood supply to the heart muscle when other tests are unclear
• Investigating certain brain conditions, such as some kinds of epilepsy or memory difficulty
• Searching for a hidden source of infection or inflammation when simpler tests have not found the answer

Risk factors

• The small risks of a PET scan are worth knowing about, though serious problems are rare:
• Pregnancy or breastfeeding, because the tracer can pass to a baby; always tell the team, as the scan may be delayed or changed
• Diabetes or high blood sugar, which can affect the quality of the pictures
• Kidney problems, which can slow how quickly the tracer leaves your body
• Feeling very anxious in small spaces, which can make lying still in the scanner hard
• Being unable to lie flat or still for the length of the scan
• Having had a reaction to a tracer or contrast dye before
• Remember that the benefit of getting a clear answer is usually much greater than these small risks, and your doctor will only request the scan if it is worthwhile.

When to see a doctor

See a doctor urgently if:

• You develop a rash, swelling, or trouble breathing after leaving the hospital, so call your local emergency number
• You have a fever, or the needle site becomes hot, red and swollen
• You feel faint, very dizzy or unwell in the hours after the scan
• You are pregnant or think you might be, and have a scan booked, so ring the imaging department before you come in

Book a routine appointment if:

• You are not sure how to prepare, or what you are allowed to eat and drink beforehand
• You take medicines for diabetes and need to know how to manage them on the day
• You feel very anxious about small spaces, or about lying still, so the team can plan ahead
• You have not received your results within the time you were told, so contact the team that arranged the scan
• You want to talk through what the results mean for your care

Diagnosis

A PET scan is done by a trained team in a hospital imaging department. They check a few things first, such as your blood sugar level and whether you could be pregnant. Then they give the tracer through a small needle in a vein, ask you to rest quietly for about an hour while the tracer spreads, and take the pictures while you lie still on a flat bed that slides through a ring-shaped scanner. A specialist doctor called a radiologist or nuclear medicine physician studies the pictures and writes a report for the doctor who sent you. The scan does not give a diagnosis on its own: it is one piece of the puzzle, used alongside your history, your examination and other tests.

Tests that may be done

• A finger-prick blood sugar check, and sometimes a blood test for kidney function
• A pregnancy test, if there is any chance you could be pregnant
• The PET scan itself, sometimes combined with a CT scan on the same machine
• Other imaging, such as an MRI or ultrasound, to add detail
• A biopsy, where a small sample of tissue is taken and checked in a laboratory, if doctors need to be certain what a growth is
• Blood tests to look at your general health and how well your organs are working

What to expect at your appointment

You will usually be asked to arrive an hour or two before your appointment. You may need to avoid eating for a few hours beforehand and to skip strenuous exercise for a day, because both can affect the pictures. Wear loose, warm clothes without metal zips or buttons, and bring a list of your medicines. After the tracer is given you will rest quietly, without talking or moving much, so the tracer can settle. The scan itself takes around 20 to 40 minutes and you need to lie still but can breathe normally. Afterwards you can eat and drink as usual. You will be asked to drink plenty of water to help flush the tracer out, and you may be given simple advice about close contact with pregnant women and small children for a few hours, depending on the tracer used.

Treatment

A PET scan is not a treatment. It is a test that helps your care team choose the right treatment for you, or check that a treatment is working. What happens next depends completely on what the scan shows and on your own situation, and your specialist team will explain the options and the reasons for them.

Self-care at home

• Follow the preparation instructions you are given, especially about fasting and about exercise the day before
• Drink plenty of water in the hours after the scan, unless you have been told to limit fluids
• Take your usual medicines unless your team tells you to change them, and never stop a medicine on your own
• Tell the team about pregnancy, breastfeeding, diabetes, kidney problems or a previous reaction to a tracer or dye
• Arrange for someone to travel home with you if you feel anxious or if you have had a sedative
• Keep the appointment letter with the phone number of the imaging department, in case you have questions
• Be kind to yourself while you wait for results, and plan something calm and enjoyable for that time

Medical treatments

Any treatment that follows will be chosen by your specialist team based on your results and your overall health. Depending on what the scan shows, options might include surgery, radiotherapy, chemotherapy or other medicines, treatments to relieve symptoms, or simply regular check-ups if nothing worrying is found. Your team will explain the benefits and downsides of each option, and you can ask questions and take your time. Your family doctor can help coordinate your care and support you between appointments.

Living with this condition

The scan day is short and the tracer leaves your body quickly, so most people get back to normal activities the same day. The bigger task is often the wait for results and the appointments that follow. Keep a notebook of questions as they come to you, and take someone with you to important appointments if you can, so there is another pair of ears.

Lifestyle tips

• Keep up your normal routine as much as you can, including gentle activity and time outdoors
• Stay hydrated, and eat regular balanced meals, especially if you have lost weight or your appetite has changed
• Limit alcohol and avoid smoking, as both can affect your health and your recovery
• Try to keep sleep regular; a wind-down routine before bed can help
• Write down questions and take them to your appointments so you do not have to hold them all in your head
• Ask a trusted friend or family member to help with practical things, such as lifts or childcare

Diet and exercise

Unless your team gives you specific advice, a normal balanced diet with plenty of vegetables, fruit, whole grains and protein is a good base. Gentle exercise such as walking, stretching or swimming can lift your mood and help you sleep. If you are recovering from treatment or feel very tired, start small and build up slowly, and ask your team whether a physiotherapist or dietitian could help.

Mental health and emotional wellbeing

It is very normal to feel anxious before a scan and while waiting for results. Some people find their mind jumps to worst-case scenarios, or feel low or irritable. These feelings usually ease once you have news and a plan. Talking to someone helps: a friend, your family doctor, or a hospital counsellor. If your worry is affecting your sleep, appetite or daily life, please tell your doctor, because support is available. If you ever feel you cannot cope or have thoughts of harming yourself, contact your local crisis line or your local emergency services straight away.

Prevention

A PET scan is not something you can prevent, and it is not something to be feared. What you can do is look after your general health, which lowers your chance of needing certain tests in the future: not smoking, keeping active, eating well, limiting alcohol, and going to the checks and screenings you are offered. If your doctor recommends a PET scan, it is because the information is likely to help; delaying it rarely helps.

Screening programmes

PET scans are not used as a general screening test for healthy people, because they can pick up harmless changes that lead to unnecessary worry and tests. Screening for some cancers and other conditions is done with other, simpler tests. Ask your doctor which screening programmes you are eligible for, as finding problems early often makes treatment simpler.

Complications

If left untreated

• A PET scan is a test, so 'not having it' is not an illness. The real question is what happens if the reason for the scan is not looked into:
• A condition such as cancer or heart disease may be found later, when treatment is harder
• Treatment may be started without full information, so it may not be the best fit for you
• A treatment that is not working may carry on longer than it needs to
• You may be left with worry and uncertainty, which is a real burden in itself

Long-term outlook

For most people a PET scan brings clarity. Sometimes it rules out a serious problem and brings relief; sometimes it gives your team the detail they need to choose the right treatment, or to change course early. Knowing what you are dealing with is the first step towards a plan, and your team will be with you at each stage.

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