What is a PET-CT Scan?

A PET-CT scan is a combination of both a CT scan and a PET scan which gives us more information on cancer conditions.
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The CT scan takes a series of x-ray images from all around the body and puts them together to create a 3-dimensional (3D) picture.
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The PET scan or a positron emission tomography scan is a type of test which uses a mildly radioactive drug to highlight the areas of your body where cells are more active than normal.
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When is a PET-CT Scan Needed?

PET-CT Scans are used to help doctors diagnose cancer and the stage of the cancer. Through the diagnosis of the cancer and its stage, doctors can determine the best course of treatment.
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Alternatively, a PET-CT scan can allow doctors to monitor how well treatments are working.
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Preparing for a PET-CT Scan

To prepare for your PET-CT scan, you will usually be asked to fast for 4 to 6 hours. You may consume water during this time but must not consume any food.
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Avoid any strenuous activities such as running or weight lifting for 24 hours before your scheduled scan. Strenuous exercise can affect the accuracy of your PET-CT scan.
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Inform staff of your medical history, including any food or drug allergies, and any drugs or supplements that you are currently taking.
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You will be asked to remove all articles of clothing with metal such as zippers or buttons and change into a hospital gown. Additionally, you will also need to remove any jewellery before the scan as metal affects the images produced.
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During a PET-CT Scan

You will be brought to the scanning room. The PET-CT machine is a large, doughnut-shaped machine.
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An intravenous line will be inserted into one of your veins, which is used to inject the radioactive substance required for the scan. You will not feel anything during this part of the procedure.
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Once the substance has been injected, you must limit your movement as too much movement may cause the substance to travel to other areas of your body, making it difficult to read the results accurately. The radioactive substance takes about 30 to 90 minutes to reach the necessary parts of your body.
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You may also be required to drink a contrast liquid or receive this through your intravenous line. The contrast liquid increases the clarity of the images taken during the scan. The contrast liquid may cause the area around your line to feel hot or itchy. There may also be a metallic taste in your mouth. Both of these feelings should subside after a few minutes. Inform staff immediately if you experience a more severe reaction, such as difficulty breathing.
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Depending on the area of your body which needs to be scanned, you will be asked to lie either on your stomach or back. However, the scan is usually done lying on your back.
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The radiographer will leave the room once you are in the right position. The table on which you are laying on will move back and forth into the machine, allowing it to take pictures. It is not very noisy, and usually, music will be played for you. The process is painless, but you may feel stiff from needing to stay still. This process should last about 30 minutes.
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The radiographer is able to see you through a TV screen or through a window, and you will be able to communicate through an intercom during the entire procedure.
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After your PET-CT Scan

The intravenous cannula will be removed. You can resume activities as per usual after your scan. You will need to drink plenty of fluids after your scan to help flush the radioactive drug from your system.
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As a precaution, for 6 hours after your scan, maintain a distance of at least one arm’s length away from pregnant women, babies, and small children.
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Risks and Side Effects

While a PET-CT scan is safe for most people, there are some groups of people who are at a higher risk of side effects.
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Pregnant women should only have a PET-CT scan in the case of an emergency. The radiation poses a risk to the unborn baby. Inform staff if you are or suspect that you could be pregnant.
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Also, let staff know if you are breastfeeding before scheduling a PET-CT scan. You may need to stop breastfeeding for a short time after having the radioactive drug and may need to express and store enough milk for your baby.
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A small bruise may form around the area where the needle was inserted. While rare, there is a risk of the tracer leaking outside of the vein, causing swelling and pain in your arm.
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Some people may develop an allergic reaction to the radioactive tracer. If you experience difficulty breathing, sweating, or weakness, inform staff immediately. This reaction is rare.
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The exposure to radiation during a PET-CT scan can slightly increase your risk of developing cancer in the future so speak to the doctor if this worries you.
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Disclaimer:
The information on the Centre For Clinical Haematology website is intended for educational use.  It should not be considered or used as a substitute for medical advice, diagnosis or treatment from a qualified health professional.