PET CT preparation

Overview

PET CT is a scan that combines two types of imaging: positron emission tomography (PET) and computed tomography (CT). The PET part shows how your cells are working, and the CT part shows detailed pictures of your organs. Preparation means the steps you need to take before the scan to make sure it goes smoothly and gives the best results.

PET CT scans are a common and widely used imaging test in hospitals, especially for people with cancer, heart conditions, or infections that are hard to diagnose.

This scan is used for people of all ages, but the preparation steps may change depending on your age, weight, and medical history. Your healthcare team will give you specific instructions.

Symptoms

Common symptoms

• PET CT scans are usually done to investigate symptoms like unexplained weight loss, persistent fever, or a lump that is not explained by other tests.

Symptoms in children

• In children, the scan may be used to look at certain types of cancer or to check how organs are working. Preparation often involves making sure the child is calm and comfortable.

Symptoms in older adults

• Older adults may need extra time to get ready, especially if they have diabetes, kidney problems, or take many medications. Always tell your doctor about all medicines and supplements.

Causes

Main causes

• A PET CT scan is ordered by a doctor when they need more information about a health problem. Common reasons include cancer staging (to see if cancer has spread), checking how well cancer treatment is working, or investigating unexplained symptoms.

Risk factors

• You may need extra preparation if you have diabetes, are pregnant or breastfeeding, have kidney problems, or are allergic to certain medications.

When to see a doctor

See a doctor urgently if:

• If you develop severe symptoms after the tracer injection, call your local emergency number immediately.
• If you have a fever or active infection on the day of the scan, contact your doctor before coming to the hospital.

Book a routine appointment if:

• If you have any questions about how to prepare, such as which medications to pause or when to eat, call the hospital's nuclear medicine or radiology department.

Diagnosis

Your doctor will explain why a PET CT scan is recommended based on your symptoms, medical history, and other test results. The scan itself is not a diagnosis – it provides images that help your doctor make a diagnosis.

Tests that may be done

• Blood tests to check your kidney function and blood sugar levels.
• A pregnancy test if you are of childbearing age.
• Sometimes a low-dose CT scan before the full scan.

What to expect at your appointment

On the day of the scan, you will arrive at the hospital. A nurse or technologist will explain the steps. You will get an injection of a sugary radioactive tracer into a vein in your arm. Then you will need to rest quietly for about 45 to 60 minutes while the tracer spreads through your body. After that, you will lie on a table that slides slowly through the scanner. You need to stay still. The scan takes about 30 minutes. Afterwards, you can go back to your normal activities. The tracer leaves your body naturally over a few hours through your urine.

Treatment

A PET CT scan is a diagnostic test, not a treatment. The results will help your doctor decide on the best treatment plan for your condition.

Self-care at home

• Drink plenty of water before and after the scan to help flush the tracer out.
• Wear comfortable clothes without metal zippers or buttons.
• Remove all jewellery and metal objects before the scan.

Medical treatments

After the scan, your doctor will review the images and discuss the results with you. Depending on what is found, you may need further tests, medications, surgery, or other treatments. Your healthcare team will explain your options.

When is surgery considered?

If the scan shows a problem that requires surgery, your surgeon will talk to you about the procedure and what to expect. The scan helps them plan the operation.

Living with this condition

The preparation for a PET CT scan is temporary. After the scan, you can resume your normal daily activities, including work, driving, and spending time with family.

Lifestyle tips

• Follow any specific instructions your doctor gives you about diet or medications on the day of the scan.
• Avoid strenuous exercise right before the scan because it can affect the results.

Diet and exercise

You will need to eat a low-carbohydrate meal the night before and then fast (no food or drinks except water) for about 6 hours before the scan. Avoid caffeine and alcohol. After the scan, you can eat normally.

Mental health and emotional wellbeing

Waiting for scan results can be stressful. It is normal to feel anxious. Talk to your healthcare team or a counsellor if you need support remembering that many conditions can be treated successfully.

Prevention

A PET CT scan is not something you need to prevent – it is a helpful tool. But you can prevent problems during the scan by following the preparation instructions carefully.

Complications

If left untreated

• Not preparing properly, such as eating before the scan, can lead to poor-quality images and may mean you need to repeat the scan.
• The tracer injection is very safe, but rare allergic reactions can occur.

Long-term outlook

With correct preparation, PET CT scans are very effective and safe. The images help your doctor make an accurate diagnosis and choose the best treatment for you. There is good reason to be hopeful.

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